Find the measure of ∠ECB.
a) 25
b) 96
c) 118
d) 146
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Answer:
Option A. ∠ECB=25°
Step-by-step 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°