Angles in isosceles triangles
The Maths Habit
Fold a sheet of paper in half. Cut a triangle across the fold, then open it out.
What do you notice about the triangle?
Two sides are equal and two angles are equal: one half lands on the other.
- Isosceles
- A triangle with two equal sides and two equal angles.
The equal angles are opposite the equal sides.
Find the size of angle x.
180 −36=144
144÷ 2 =72
x =72°
180 −124=56
56÷ 2 =28
x =28°
180 −36=144
144÷ 2 =72
x =72°
65+65=130
180 −130=50
x =50°
180 −36=144
144÷ 2 =72
x =72°
180 −48=132
132÷ 2 =66
x =66°
180 −36=144
144÷ 2 =72
x =72°
34+34=68
180 −68=112
x =112°
180 −36=144
144÷ 2 =72
x =72°
180 −106=74
74÷ 2 =37
x =37°
An isosceles triangle has one angle of 100°. Find the other two angles.
40° and 40°An isosceles triangle has one angle of 50°. Find both possible pairs for the other two angles.
50°, 80° or 65°, 65°
