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Find the number of degrees in arc AB of the figure below if segments PA and PB are secants; AEC = 115, BFD = 130, and P = 30
Find The Number Of Degrees In Arc AB Of The Figure Below If ...
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Options:
Answer: Option A
:

Angle AEC=115. Suppose there is a point X in the major segment of chord AC. AECX will be a cyclic quadrilateral. Therefore , Angle AEC + Angle AXC =180


Angle AXC= 65


Angle AOC=130 (Measure of arc AC at the centre O)


Similarly Angle BOD = 100


Therefore, Angle AOB (or measure of arc AB) + Angle COD (or measure of arc CD)= 360 - (100+130) = 130 ---- (1)


Now we know the theorem that if there are two secants PA and PB and P lies outside the circle , then Angle P = 12 ( measure of arc COD - measure of arc AOB) =30 (given in the ques) -- (2) ( measure of arc CD - measure of arc AB) =60 -- (3)


You can see that equations (1) and (3) are simultaneous equations in measure of arc AB and measure of arc CD .So, finally measure of arc AB is (130+60)2 = 95.



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