How to find the angles of an isosceles triangle given three sides?


Question: How to find the angles of an isosceles triangle given three sides

An isosceles triangle is a triangle that has 2 sides of equal length

Answer: The angles of an isosceles triangle with three given sides can be found using the law of cosines

Let us see how to get the angles using cosine law

Explanation:

From cosine's law

cos C = (a² + b² - c²)/2ab

cos A = (b² + c² - a²)/2bc

cos B = (c² + a² - b²)/2ca

Here, assuming b = c            (Since, it's an isosceles triangle)

cos A = (2b² - a²)/2b²

cos B = cos C = a/2b

Hence, we can use law of cosines to find the angles when three sides are given