Geometry & MeasuresStudy Notes

Worked Example 1: Finding a Side

Part of Trigonometry (SOH CAH TOA)GCSE Mathematics

This study notes covers Worked Example 1: Finding a Side within Trigonometry (SOH CAH TOA) for GCSE Mathematics. Revise Trigonometry (SOH CAH TOA) in Geometry & Measures for GCSE Mathematics with 19 exam-style questions and 7 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 4 of 6 in this topic. Use this study notes to connect the idea to the wider topic before moving on to questions and flashcards.

Topic position

Section 4 of 6

Practice

19 questions

Recall

7 flashcards

Worked Example 1: Finding a Side

A right-angled triangle has an angle of 35° and the hypotenuse is 10 cm. Find the opposite side.

Step 1 Label and identify

We have: angle = 35°, H = 10 cm

We need: O = ?

O and H → use Sin

Step 2 Write the formula

sin 35° = O10

Step 3 Rearrange for O

O = 10 × sin 35°

O = 10 × 0.5736...

O = 5.74 cm (2 d.p.)

Answer: 5.74 cm

Keep building this topic

Read this section alongside the surrounding pages in Trigonometry (SOH CAH TOA). That gives you the full topic sequence instead of a single isolated revision point.

Practice Questions for Trigonometry (SOH CAH TOA)

Which trigonometric ratio connects the opposite side and the hypotenuse in a right-angled triangle?

  • A. tan θ = opposite / adjacent
  • B. cos θ = opposite / hypotenuse
  • C. sin θ = opposite / hypotenuse
  • D. sin θ = adjacent / hypotenuse
1 markfoundation

For the triangle shown, a student chooses to use sin to find the missing side. Explain why they chose sin rather than one of the other trigonometric ratios.

2 marksstandard

Quick Recall Flashcards

SOH CAH TOA
sin = Opp/Hyp, cos = Adj/Hyp, tan = Opp/Adj
SOH CAH TOA
Sin = O/H, Cos = A/H, Tan = O/A. Pick based on which two sides you have or need.

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