Question

​Quadrilateral ABCD​ is inscribed in this circle.

What is the measure of angle C?
Enter your answer in the box.

Answer 1

C = 80

Explanation:

A cyclic quadrilateral is one where all 4 vertices touch the circumference of a circle.

It has 1 interesting property that should concern you: <B + <D = 180 degrees.

3x - 59 + 2x - 1 = 180 Combine like terms

5x - 60 = 180 Add 60 to both sides.

5x = 180 + 60

5x = 240

x = 240/5

x = 48

Now go to 2x + 4.

x = 48

A = 2*48 + 4

A = 96 + 4

A = 100

So C = 180 - 100

C = 80