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 7 in this topic. Use this study notes to connect the idea to the wider topic before moving on to questions and 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.)
Practice questions for Trigonometry (SOH CAH TOA)
Which trigonometric ratio connects the opposite side and the hypotenuse in a right-angled triangle?
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.