Geometry & MeasuresKey Facts

The Formula

Part of Area of Triangle (Trig) · GCSE GCSE Mathematics revision

This key facts covers The Formula within Area of Triangle (Trig) for GCSE Mathematics. Revise Area of Triangle (Trig) in Geometry & Measures for GCSE Mathematics with 12 exam-style questions and 2 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 2 of 4 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.

Topic position

Section 2 of 4

Practice

12 questions

Recall

2 flashcards

The Formula

Area	= (1/2) × a × b × sin C
Where	C is the INCLUDED angle (between sides a and b)
Also written as	(1/2)ab sinC or (1/2)bc sinA or (1/2)ac sinB

Keep building this topic

Read this section alongside the surrounding pages in Area of Triangle (Trig). That gives you the full topic sequence instead of a single isolated revision point.

No Height? No Problem!Worked Example Knowledge Organiser: Area of Triangle Using Trigonometry

Practice Questions for Area of Triangle (Trig)

What is the trigonometric formula for the area of a triangle with sides a and b and included angle C?

A. Area = ab sinC
B. Area = ½ab sinC
C. Area = ½ab cosC
D. Area = ½(a + b) sinC

1 markfoundation

Starting from Area = ½ × base × height, show how to derive the formula Area = ½ab sinC.

2 marksstandard

Quick Recall Flashcards

Trig Area Formula

Area = (1/2)ab sinC. The angle MUST be between the two sides you're using.

Area with Trig

Area = ½ab sin C

12 questions on Area of Triangle (Trig) — practise free

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Worked Example