Question

What is the measure of arc DE?

*HINT - you'll have to use inverse trig FIRST by looking at the right triangle to find the measure of
**ROUND ALL ANSWERS TO THE NEAREST WHOLE DEGREE!

Answer 1

17.06

Explanation:

for every right triangle with vertices on the same circle perimeter, the hypotenusa must be the diameter

dia. = 12 cm

radius = 12 ÷ 2 = 6 cm

CD² = CE² + DE²

12² = 9.09² + DE²

DE² = 144 - 82.6281

DE² = 61.3719

DE² = EF² + FD² - 2(EF)(FD)cos∠EFD

61.3719 = 6² + 6² - 2(6)(6)cos∠EFD

cos∠EFD = 0.1476

∠EFD = 81.5114°

arc ED = 81.5114°/360° × circle perimeter

= 81.5114°/360° × 3.14 × 12

= 17.06