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In circle O, AD ⊥ BC and the m ∠ACB = 65º . What is the measure of angle OBD?

a.100

b. 80

c. 50

d. 40



 

 May 11, 2020
 #1
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Angle(ACB) is inscribed in minor arc(AB), therefore arc(AB) = 2·angle(ACB).

 

Since angle(ACB) = 65o, arc(AB) = 130o.

 

Arc(AB) = central angle(AOB)   --->   angle(AOB) = 130o.

 

This makes angle(BOC) = 50o.

 

So, angle(OBD) = 40o.

 May 11, 2020

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