# In an isosceles triangle, the apex angle is 70 degrees. What are the other angles equal to?

September 24, 2021 | education

| An isosceles triangle is a triangle in which two sides are equal, and the angles are also equal at the third, not equal to the other two, side. The third side is called the base, and the equal sides are called the sides.

Let a, b and c – angles of an isosceles triangle (a = c – angles at the base). The triangle sum theorem says that the sum of all interior angles of any triangle is 180 degrees, then:

a + b + c = 180 degrees.

Let’s denote a and c as x, then:

x + 70 + x = 180;

2x = 180 – 70;

2x = 110;

x = 110/2;

x = 55.

Angles a and c are equal to 55 degrees.

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