If angle C is a right angle and angle A equals 50º, then prove that the measure of angle B equals 40º. Which of the following would be the first step to assume in order to prove the statement above by contradiction using an indirect proof?
The measure of angle B equals 40º.
Angle C is not a right angle.
The measure of angle A equals 50º.
Angle C is a right angle.
The measure of angle B does not equal 40º.
