Points D,E,F lie on circle O such that the line tangent to O at D intersects ray EF at P. Given that PD=4,PF=2, and ∠FPD=60∘, determine the area of circle O.
A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.
Solution
By the power of a point on P, we get that 16=PD2=(PF)(PE)=2(PE)⇒PE=8. However, since PE=2PD and ∠FPD=60∘, we notice that PDE is a 30−60−90 triangle, so DE=43 and we have ED⊥DP. It follows that DE is a diameter of the circle, since tangents the tangent at D must be perpendicular to the radius containing D. Hence, the area of the circle is (21DE)2π=12π
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