#### • Class 11 Physics Demo

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#### • how to find the coterminal angle

Question:I know what coterminal angles are, but when do I subtract 2 pi/360 degrees or add 2 pi/360 degrees to find the positive coterminal angle? What about the negative coterminal angle?

Answers:If you graph angles x = 30 and y = - 330 in standard position, these angles will have the same terminal side. Coterminal angles Ac to angle A may be obtained by adding or subtracting k*360 degrees or k* (2 ). Hence: Ac = A + k*360 if A is given in degrees. or Ac = A + k*(2 ) if A is given in radians. where k is any negative or positive integer. A positive coterminal angle to angle A may be obtained by adding 360 , 2(360) = 720 (or any other positive angle multiple of 360 ) . A negative coterminal angle to angle A may be obtained by adding -360 , -2(360) = -720 (or any other negative angle multiple of 360 ).

Question:

Answers:You can find coterminal angles by adding and subtracting 360 300 - 360 = -60 300 + 360 = 660 You can find others by continuing to add and subtract 360 (one complete revolution of the circle)

Question:I forgot how to do it. Please respond as fast a you can. Thanks! :)

Answers:2 pi is about 6.28, so this angle is between -2pi and -4pi. If we rotate -4 pi, then rotate in the positive direction to get back to -10, the positive rotation is -10 - (-4pi) = 4 pi - 10 = roughly 2.56. You can find it more accurately than that.

Question:I'm supposed to find the coterminal angles (one positive and one negative) for the given angle and supply my answer in radians. a) (8pi)/9 b) (8pi)/45 I just have no idea how to do this so if you could show me that would be great.

Answers:8pi/9 - 2pi = -10pi/9 8pi/45 - 2pi = -82pi/45