Question

Suppose ΔDEF has an exterior angle at vertex D. The measure of the exterior angle is (8x−2)º, m∠E=(3x−8)°, and m∠F=(4x+13)°. What is the measure of the exterior angle at vertex D?
A. 7°
B. 13°
C. 41°
D. 54°

Answer 1

The measure of the exterior angle at vertex D is: D. 54°

Recall:

• The exterior angle theorem of a triangle states that the measure of an exterior angle equals the sum of the measures of two opposite interior angles of the triangle.

Thus:

In ΔDEF, (8x−2)º is an exterior angle at vertex D.

m∠E = (3x−8)° (interior angle)

m∠F = (4x+13)° (interior angle)

Therefore:

(8x−2)º = (3x−8)° + (4x+13)°

• Solve for x

8x - 2 = 3x - 8 + 4x + 13

• Combine like terms

8x - 2 = 7x + 5

8x - 7x = 2 + 5

x = 7

Exterior angle at vertex D = (8x−2)º

• Plug in the value of x

= 8(7) - 2

= 54º (option D)

Learn more about exterior angle theorem on:

brainly.com/question/24756010