For each of the following, the given angle is the base angle of an isosceles triangle. Find the third angle of the triangle. a) 40°
b) 87°
c) 15°
d) 79°

Isosceles triangle , 2 base angles are equal .sum of all angles of a triangle = 180°
180°-2 ( base angles )

a) 180°-2(40°)
=180°-80°
= 100°

b) 180°-2(87°)
= 180°-174°
=6°

c) 180°-2(15°)
= 180°-30°
= 150°

d) 180°-2(79°)
=180°-158°
= 22°