Prove that the sum of two acute angles of a right triangle is 90 °.

By condition, a right-angled triangle is given.
Let’s designate this triangle ABC.
Angle A in it is right, and angles B and C are sharp.
Let us prove that B + C = 90 °.
It is known that the sum of all the angles of a triangle is 180 °.
Thus, we can write:
A + B + C = 180 °.
Angle A = 90 °, therefore:
90 ° + B + C = 180 °.
B + C = 180 ° – 90 °.
B + C = 90 °.
Thus, the sum of two acute angles of a right-angled triangle is 90 °, as required.