Question

The following are base angles of isosceles triangles. In each case, what is the third angle of the isosceles triangle: (a) 64 (b) 42 (c ) 18 (d) 82?

Answer 1

An isosceles triangle has two congruent base angles `B` and an apex angle `A`. We know `A+B+B=180^circ` or `A=180^circ - 2 B`. So (a) `A=180-2(64)=52 ^\circ` (b) `A=180-2(42)=96 ^\circ` (c) `180-2(18)=144 ^\circ` (d) `180-2(82)=16 ^\circ .`