Find a cofunction with the same value as sec(9π/20). Write your answer below with the angle expressed in radian(s).

Answer 1

The cofunction of an angle is the compliment of the angle.

In this case the formula is:. Csc(angle) = Sec(PI/2 - angle)

Put in the values: Csc(9PI/20) = Sec(PI/2 - 9PI/20)

Use common denominator: Sec(10PI/20 - 9PI/20) = Sec(PI/20) in radians

If you convert the radians to degrees the two angles are 81 and 9 which are complimentary angles.

Answer 2

Sec(9π/20) = 1/Cos(9π/20) = 1.0125

9π/20 = 1.4137 radians = 81°

81º is the same as -279º or -4.8695 radians

Then the cofunction is Sec(-279º) or Sec(-4.8695)