The points A , B , C are on a circumference, where O is the center, and P is the intersection point of A C and B O , as shown above.
If ∠ A B P = 4 9 ∘ and ∠ P C O = 1 7 ∘ , what is the value of ∠ B P C in degrees?
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@Worranat Pakornrat Hats off , sir !👌🙇
Sorry, I really find this confusing... only if someone had a video in this
Joining OA, We see that both the blue angles are equal and so are the 2 yellow angles. (By isoceles triangle theorem since radii are equal)
So , Using exterior angle theorem in triangle P A B , We get R e d = 2 Y e l l o w − B l u e
Thus R e d = 2 ∗ 4 9 − 1 7 = 9 8 − 1 7 = 8 1
Upper image for diagram
Lower image for solution.. easy to understand
1) OBC Is an isosceles triangle.
2) 2(Angle BAC) = Angle BOC.
Let us take Angle BAC=θ.
So angle BOC =2θ.
Took me a few mins how you got 90 - theta and 72 - theta, but that's from your last remark :) nice solution.
Actually it is 73-theta , not 72 - theta @Peter van der Linden
Since BAP and BOC cut the same arc, BAP = 1/2 * BOC
BPC = BAP + 49 = BOC + 17 because an exterior angle = sum of the two non adjacent angles
Substituting 1/2*BOC + 49 = BOC + 17
Solving BOC = 64
64 + 17 = 81 degrees
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Since ∠ A P B + ∠ B P C = 1 8 0 ∘ , then ∠ B P C = ∠ B A P + ∠ A B P = ∠ B A P + 4 9 ∘ .
Thus, we are attempting to find ∠ B A P for a solution, and we can do so by extending the O C line to meet point D on the circumference before joining it with point B , as shown below:
According to Inscribed Angles Theorem , ∠ B A P = ∠ B D O , and because △ B D O is an isosceles triangle, ∠ D B O = ∠ B D O .
Furthermore, from Inscribed Angles Theorem , ∠ A B D = ∠ A C D = 1 7 ∘ .
Thus, ∠ A B P = 4 9 ∘ = ∠ A B D + ∠ D B O = 1 7 ∘ + ∠ B A P .
Hence, ∠ B A P = 4 9 ∘ − 1 7 ∘ = 3 2 ∘ .
Finally, ∠ B P C = 4 9 ∘ + 3 2 ∘ = 8 1 ∘ .