Question

If m∠A = (3x-6)° and m∠B = (x + 9)°, find the m∠D.

A) 32°
B) 39°
C) 41°
D) 49°
E) None of the above

Answer 1

Because line BD goes through the center of the circle Angle A is a right angle which equals 90 degrees.

Set the equation for A to equal 90 and solve for x:

3x-6 = 90

Add 6 to each side:

3x = 96

Divide both sides by 3:

x = 32

Now we have a value for x , use that to solve for angle b:

B = x +9 = 32 + 9 = 41 degrees.

Now we know A and B, we can solve for D.

The three inside angles of a triangle need to equal 180.

D = 180 - 90 - 41 = 49 degrees.

The answer is D) 49