Shadowing Practice: GCSE Maths - Alternate, Corresponding and Allied Angles - Parallel Lines Angle Rules (2026/27 exams) - Learn English Speaking with Video
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Thank you.
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In this video, we're going to cover how you can use the rules of alternate angles, corresponding angles, and allied angles.
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Importantly though, we only use these rules in one specific scenario.
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which is where we have two parallel lines running alongside each other like this, and then another line, which we can call a transversal, cutting through them both.
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Whenever this happens, we end up with two groups of angles.
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One here at the bottom, and another one here at the top.
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And there are four important points that you want to notice about these angles.
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The first is that both groups of angles are both exactly the same.
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For example, in this case, they both have a 120 degree, a 60 degree, another 120 degree, and another 60 degree angle.
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The second point is that each group only contains two different angles.
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In this case, 60 degree angles.
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and 120 degree angles.
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The third point is that the two different angles will always add up to 180 degrees.
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For example here, where our angles are 60 degrees and 120 degrees, These two add up to 180 degrees.
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And the last point is that vertically opposite angles are always the same.
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For example, these two 60 degree angles are considered vertically opposite which is why they're both 60 degrees.
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and likewise these two 120 degree angles are also vertically opposite.
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Now, as long as you properly understand all of these rules, You can use this knowledge to work out unknown angles if one of them is missing.
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For example, if we had to find this angle here, marked x.
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we'd be able to tell that it's 60 degrees.
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Either because it's opposite this 60 degree angle, and we know that vertically opposite angles are always equal,
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or because we know that it has to add to this 120 degrees to make 180.
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To help with more complicated questions though, there are three more rules that are worth memorizing.
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The first rule is that alternate angles are the same.
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And what I mean by alternate angles is the two angles found in the corners of a Z shape like this.
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For example, if we look at our diagram, we can see that the Z shape is here.
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even though it's been flipped around in this case.
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And so it's these two 60 -degree angles that we consider alternate angles.
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The second rule is pretty similar, but says that corresponding angles are the same.
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and corresponding angles are these two angles that you find in an F shape.
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For example, on our diagram, the F shape is here.
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So these two 60 degree angles are corresponding angles.
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The third rule is that allied angles add up to 180 degrees.
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and allied angles are just the interior angles of a C shape.
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So in this diagram, these two angles would add together to make 180 degrees.
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We also sometimes call these co -interior angles, or just interior angles.
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So just know that allied, co -interior and interior all mean the same thing here.
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If we look on our main diagram, we can see one of these C shapes here.
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So the allied angles would be this 60 degrees, and this is 120 degrees.
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which indeed do add together to make 180.
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One thing to point out with all of these rules is that you'll sometimes see them in other orientations.
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like flip it around, in which case they'll be harder to spot.
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But as long as they have the same combination of two parallel lines and one transversal, then the rules are going to be the same.
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To see how it all works in practice, let's have a go at this exam question.
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So in this question we have a pair of parallel lines
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AB and CD and then a transversal that cuts through the two of them.
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and we need to find the missing angles x and y Now, because of all of the different rules that we can use, there are normally multiple ways that we can do questions like this.
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And so there's no one correct way of doing it.
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The way I would do it though is notice that this section here is like a backwards C shape.
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and do the 135 degrees and the x are allied or co -interior angles.
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which means that they must add together to make 180 degrees.
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So we now know that 135 plus x equals 180.
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which means that x is 45 degrees.
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And then because y is vertically opposite x, we know that y must be 45 degrees as well.
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Anyway, that's the end of this video.
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So like always, if you want to practice questions on any of this stuff, then head over to our platform.
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If you want to go to this particular lesson, then click on the link down in the description below.
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Or if you want to see our platform in general, then click on the link in the top right corner of this screen.
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Otherwise, we'll see you next time.
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Vocabulary and speaking notes for this lesson
This B1 speaking lesson is built on the video “GCSE Maths - Alternate, Corresponding and Allied Angles - Parallel Lines Angle Rules”. The speaker keeps coming back to these words: angle, degree, rule, shape, add. This video has 59 sentences and 817 words to shadow. The speech runs for 5:34. The speaker talks at a steady 147 words per minute, a comfortable pace for shadowing. 86% of the words are among the 3,000 most common in English; the rest is worth studying before you start.
Key vocabulary in this video
The 15 most advanced words in the video, with pronunciation and meaning:
| Word | Pronunciation | Meaning |
|---|---|---|
| ally noun | /ˈæl.aɪ/ | A person who co-operates with or helps another; an associate; a friend. |
| vertically adverb | /ˈvɝ.tɪ.kəli/ | In a vertical direction or position. |
| correspond verb | /ˌkoɹəˈspɑnd/ | To be equivalent or similar in character, quantity, quality, origin, structure, function etc. |
| diagram noun | /ˈdaɪ.ə.ɡɹæm/ | A plan, drawing, sketch or outline to show the function or operation of something, or to show the relationships between the parts of a whole. |
| alternate adjective | /ˈɔl.tɚ.nət/ | Happening by turns; one following the other in succession of time or place; first one and then the other (repeatedly). |
| transversal noun | /tɹænsˈvɝsəl/ | A line which traverses or intersects any system of other lines transversely. |
| parallel adjective | /ˈpæ.ɹəˌlɛl/ | Equally distant from one another at all points. |
| flip verb | /flɪp/ | To throw so as to turn over. |
| memorize verb | /ˈmɛm.əˌɹaɪ̯z/ | To fully learn so as to have entirely available to the memory; to learn by heart, commit to memory. |
| backward adjective | /ˈbækwɚd/ | Situated toward or at the rear of something. |
| likewise adverb | /ˈlaɪkˌwaɪz/ | In a similar manner. |
| orientation noun | /ˌɔː.ɹi.ənˈteɪ.ʃən/ | The determination of the relative position of something or someone. |
| importantly adverb | /ɪmˈpɔɹ.tənt.li/ | Used to mark a statement as having importance. |
| scenario noun | /sɪˈnɛəɹioʊ/ | An outline or model of an expected or supposed sequence of events. |
| examination noun | /ɪɡˌzæm.ɪˈneɪ.ʃən/ | The act of examining. |
Phrasal verbs you will hear
| Word | Pronunciation | Meaning |
|---|---|---|
| add up to verb | To have a particular effect in combination. | |
| cut through verb | To take a shortcut through. | |
| work out verb | /ˌwɝk ˈaʊt/ | To calculate. |
Grammar in this video
The structures the speaker uses most, with the exact words from the video:
| Structure | In the video |
|---|---|
| Passive voice be + past participle — the focus is on what happens, not who does it | are considered · been flipped · are allied |
| Future with “will” will + verb — a decision, promise or prediction | will always add · you'll sometimes see · they'll be |
| Obligation: must / have to / need to saying that something is necessary | had to find · has to add · need to find |
| Present continuous am/is/are + -ing — something happening right now or around now | is missing · are corresponding |
Pronunciation to watch
The speaker uses 6 contractions and reduced forms, such as they'll, they're, we'd. Say them the short way, as you hear them.
- The “sh” and “zh” sounds: orientation /ˌɔː.ɹi.ənˈteɪ.ʃən/, examination /ɪɡˌzæm.ɪˈneɪ.ʃən/
- Long words — get the stress right: vertically /ˈvɝ.tɪ.kəli/, orientation /ˌɔː.ɹi.ənˈteɪ.ʃən/, importantly /ɪmˈpɔɹ.tənt.li/, examination /ɪɡˌzæm.ɪˈneɪ.ʃən/
How to practise with this video
- Listen to the whole video once without speaking and note the words you do not know.
- Shadow it sentence by sentence at normal speed, repeating each one until your rhythm matches the speaker.
- Record yourself and compare with the original, paying attention to words like ally, vertically, correspond.
What is the Shadowing Technique?
Shadowing is a science-backed language learning technique originally developed for professional interpreter training and popularized by polyglot Dr. Alexander Arguelles. The method is simple but powerful: you listen to native English audio and immediately repeat it out loud — like a shadow following the speaker with just a 1–2 second delay. Unlike passive listening or grammar drills, shadowing forces your brain and mouth muscles to simultaneously process and reproduce real speech patterns. Research shows it significantly improves pronunciation accuracy, intonation, rhythm, connected speech, listening comprehension, and speaking fluency — making it one of the most effective methods for IELTS Speaking preparation and real-world English communication.