Question

If a triangle has sides of length 8cm, 8cm, and 5cm, how do I find the measure of the angle between the two equal sides?

Answer 1

Use the cosine rule to find the angle as `36,42^@`.

Explanation:

The cosine rule states that for a triangle of sides `a, b, and c`, and with angle `theta` opposite side `a`, the following relationship holds :

`a^2=b^2+c^2-2bc cos theta`.

Applying this rule to the given problem yields :

`5^2=8^2+8^2-2*8*8*cos theta`

`therefore theta= cos^(-1)((25-2*64)/(-128))=36,42^@`.