Question

For which side has length 3cm, another side has length 4cm and the included angle is 110 degrees. What is the length of the third side to the nearest mm

Answer 1

58mm

Explanation:

We can solve this kind of problem by using cosine rule:

a² = b² + c² - 2*b*c*cosA

In this question,

b = 3cm

c = 4cm

A = 110°

Hence,

a² = 3² + 4² - 2*3*4*cos110

a² = 9 + 16 - 24cos110

a² = 25 - (-8.208)

a² = 33.208

=> a = 5.763 cm

Approximately (in mm), a = 58mm

(10mm = 1cm)