Question

Find the measure of ∠ECB.

a) 25
b) 96
c) 118
d) 146

Answer 1

25

Explanation:

Answer 2

Option A. ∠ECB=25°

Explanation:

we know that

The measurement of the outer angle is the semi-difference of the arcs it encompasses.

so

∠ECB=(1/2)[arc DB-arc EB]

substitute the given values

(x+10)°=(1/2)[146°-(6x+6)°]

solve for x

2x+20=140-6x

2x+6x=140-20

8x=120

x=15

Find the measure of angle ECB

∠ECB=x+10=15+10=25°