Find the third corner of a triangle if the two angles are 20 degrees and 70 degrees.

From the condition, we know the degree measure of the two angles of the triangle and it is equal to 20 ° and 70 °.

In order to find the degree measure of the third angle of a triangle, let’s recall the theorem on the sum of the angles of a triangle.

It says that the sum of the angles of the triangle is 180 °.

Let us denote by the variable x the degree measure of the third angle and solve the linear equation:

x + 20 + 70 = 180;

Move the terms without a variable to the right side of the equation:

x = 180 – 20 – 70;

x = 180 – 90;

x = 90 °.

So the third angle of the triangle is 90 °.