In the figure, ab=12, bc=8, de=6, pd=4, and a is the point of tangency. find the radius of circle p.

The radius of the circle P = 2√10 = 6.325

Step-by-step explanation:

∵ AB is a tangent to circle P at A

∴ (AB)² = BC × BE

∵ BC = 8 , AB = 12 , ED = 6

∵ BE = ED + DC + CB

∴ BE = 6 + CD + 8 = 14 + CD

∴ (12)² = 8 × (14 + DC) ⇒ (12)²/8 = 14 + CD ⇒ CD = (12)²/8 - 14

∴ CD = 4

Join PC and PE (radii)

In ΔBDC and ΔPDE ⇒ ∵ ∠PDC = Ф , ∴ ∠PDE = 180 - Ф

Use cos Rule:

∵ r² = (PD)² + (DC)² - 2(PD)(DC)cosФ

∴ r² = 16 + 16 - 32cosФ = 32 - 32cosФ ⇒ (1)

∵ r² = (PD)² + (DE)² - 2(PD)(DE)cos(180 - Ф) ⇒ cos(180 - Ф) = -cosФ

∴ r² = 16 + 36 + 48cosФ = 52 + 48cosФ ⇒ (2)

∵ (1) = (2)

∴ 32 - 32 cosФ = 52 + 48cosФ

∴ 32 - 52 = 48cosФ + 32cosФ

∴ -20 = 80cosФ

∴ cosФ = -20/80 = -1/4

∴ r² = 32 - 32(-1/4) = 32 + 8 = 40

∴ r = √40 = 2√10 = 6.325

829 feet per second is your answer. You do this by doing 9,944in/s x ft./12in. Cancel out the in., and multiply to get 9,944ft in 12 seconds. Divide 9,944 by 12 to get around 828.6 ft., and then then round it up to get 829 ft. per second.