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GR.7.3

Find lengths in right-angled triangles

Recall and use trigonometric ratios to find lengths in right-angled triangles

3 hand-picked video lessons for this topic, each checked for relevance and clarity, graded by difficulty and labelled by depth. Press play to watch — nothing loads from YouTube until you do.

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Grade 3–7 Core 🇬🇧 UK

Trigonometry (SOHCAHTOA) - GCSE Maths

1st Class Maths 400K views

Thorough UK GCSE lesson with five worked examples on finding missing sides, including the tricky denominator case.

Jump to 0:10Labelling a right-angled triangle 1:49What are sin, cos and tan?3:35Example 1 - missing side 6:04Example 2 - missing side 7:22Example 3 - missing side 8:31Example 4 - missing side but x on denominator

Grade 3–6 Core 🇬🇧 UK

Trigonometry Missing Sides - Corbettmaths

corbettmaths 151K views

Corbettmaths clearly demonstrates finding missing sides given a side and an angle.

Grade 3–6 Core 🇬🇧 UK

Trigonometry | SOH CAH TOA | Sin, Cos, Tan

Cognito 509K views

Clear UK walkthrough of labelling sides and using SOH CAH TOA to find a missing length.

Jump to 0:28Labelling Sides 1:37Introduction to Trigonometric Ratios (Sin, Cos, Tan)2:05Using SOH CAH TOA 5:57Example 2: Finding an Unknown Side