What is the cosine rule?

What is it?The cosine rule is a tool to find the size of an angle or the length of a side in a triangle.When to use it?- When we are given 2 sides and an angle- When we are given 3 sidesHow?For a triangle with sides a,b and c and angles A, B and C the cosine rule can be written as:a2 = b2 + c2 - 2bc cos Aorb2 = a2 + c2 - 2ac cos Borc2 = a2 + b2 - 2ab cos C

NG
Answered by Naomi G. Maths tutor

4981 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

Solve the simultaneous equations 3x+2y=4 and 4x+5y=17 for x and y


Fully simplify this equation; 3x^3 - x(3x+36) = 0


I don't understand how to solve quadratic inequalities?


There are 10 boys and 20 girls in a class. The class has a test. The mean mark for all the class is 60. The mean mark for the girls is 54. Work out the mean mark for the boys.


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

MyTutor is part of the IXL family of brands:

© 2025 by IXL Learning