Question

The length of two sides of triangle 2 units and 3 units the angle between them is 60 the length of third angle is

Answer 1

Let the triangle be named ABC.

Let AC = b = 2, AB = c = 3, and angle A = 60 degree.

We have to find BC = a.

Using law of cosines,

a^2 = b^2 + c^2 - 2bc • cos A

a^2 = 2^2 + 3^2 - 2 • 2 • 3 • cos 60

a^2 = 4 + 9 - 12 • 1/2

a^2 = 13 - 6

a^2 = 7

a = 7^(1/2) [square root of 7]