Question

In a triangle with vertices A,B and C, if C =64° and the lengths AC= 40mm and BC= 70mm find the length AB using cosine rule

Answer 1

63.6mm

Explanation:

According to cosine rule;

AB² = BC²+AC²-2(BC)(AC)cos m<C

Substitute the given values

AB² = 70²+40²-2(70)(40)cos 64

AB² = 4900+1600-5600cos64

AB² = 6500-5600(0.4384)

AB² = 6500-2,454.87

AB² = 4,045.12

AB = √4,045.12

AB = 63.6mm

Hence the length of AB is 63.6mm