The sides of a triangle are 9, 12, and 15 centimeters long. what is the angle between the 2 shortest sides?

Use this following formula to solve the problem

a² + b² - (2ab) cos C = c²

From the question, we can determine

a = 9

b = 12

c = 15

and the question is the angle C (angle between a and b)

Input the numbers between the formula

a² + b² - (2ab) cos C = c²

9² + 12² - (2 * 9 * 12) cos C = 15²

81 + 144 - 216 cos C = 225

225 - 216 cos C = 225

-216 cos C = 0

cos C = 0

∠C = 90°

Angle between the 2 shortest sides is 90°