Which of the following statements is false? A. Two circles are congruent if and only if they have the same radius.
B. The product of two numbers is even if and only if both numbers are even.
C. Today is Monday if and only if yesterday was Sunday.
D. Two lines are parallel if and only if they have the same slope.

C is false

Step-by-step explanation:

Example 3 is odd but 6 is equal.

3•6 is 18

18 is even

proofs involving isosceles triangles often require special consideration because an isosceles triangle has several distinct properties that do not apply to normal triangles.(more about triangle types) therefore, when you are trying to prove that two triangles are congruent, and one or both triangles, are isosceles you have a few theorems that you can use to make your life easier.

step-by-step explanation:

an isosceles triangle has two congruent sides and two congruent angles. the congruent angles are called the base angles and the other angle is known as the vertex angle. ∠bac and ∠bca are the base angles of the triangle picture on the left. the vertex angle is ∠abc