GCSE Revision Notes, Resources      

GCSE Maths > Trigonometry - Sine and Cosine Formula

The Sine Rule

The sine rule is an important rule relating the sides and angles of any triangle (it doesn't have to be right-angled!):

If a, b and c are the lengths of the sides opposite the angles A, B and C in a triangle, then:

a

=

b

=

c

sinA sinB sinC


If you wanted to find an angle, you can write this as:

sinA

=

sinB

=

sinC

a

b

c

The Cosine Rule

This also works in any triangle:

c = a + b - 2abcosC
which can also be written as:
a = b + c - 2bccosA

The area of a triangle

The area of any triangle is absinC (using the above notation).
This formula is useful if you don't know the height of a triangle (since you need to know the height for base height).

Copyright Matthew Pinkney 2003

Site Search:


Copyright © 2004-2013 revisioncentre.co.uk In association with: Computer Science Revision | Revision Links and Tutors | EFL Teaching / Learning
Navigation: Home | Contact | KS2 Maths | Advice | Parents | Games | Shop | Links |
GCSE Subjects: Biology | Chemistry | Computing | English | French | Geography | German | History | Maths | Physics | RE | Spanish
Web Hosting by Acuras