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∘
___
:
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.
Was this answer helpful ?
Submit Solution