Question

In the diagram, AB = AC = 10 and angle A = 60 degrees. Find BC.

Answer 1

Explanation:

AB = AC (= 10) makes this an isoceles triangle (both legs are equally long).

that means asks the angles B and C must be equal.

and because the sum of all angles in a triangle is always 180°, we get

180 = 60 + B + C = 60 + 2B

120 ÷ 2B

B = 60° = C

so, all 3 angles are equal and 60°, so that makes this triangle even an equilateral triangle (all 3 sides are equally long).

therefore,

BC = 10