# Co terminal Angle?

• Jun 19th 2005, 10:39 AM
Justardms
Co terminal Angle?
I need to find a positive co-terminal angle for 120 deg. and one for pie/5
and a negative co-terminal angle for 420 deg. and one for 3 pie/5
• Jun 20th 2005, 04:12 AM
ticbol
Positive angle that is co-terminal with 120 deg.
One of them is (120 +360) = 480 degrees. ---answer.
Everytime you do 1 revolution (360 deg), you will get one more.

Positive angle that is co-terminal with pi/5.
In radians, 1 revolution is 2pi, so,
One of them is (pi/5 +2pi) = (pi +10pi)/5 = 11pi/5 ---answer.
Everytime you do 1 revolution (2pi), you will get one more.

Negative angle that is co-terminal with 420 deg.
420 deg is (360 +60) deg. It is is the 1st quadrant.
So, measuring clockwise, -360 +60 = -300 degrees ----answer.
Everytime you do 1 revolution (-360deg), you will get another one.

Negative angle that is co-terminal with 3pi/5.
3pi/5 is 0.6pi. It is more than pi/2, but less than pi, so it is in the 2nd quadrant.
Meausing clockwise, -2pi +(3pi/5) = (-10pi +3pi)/5 = -7pi/5 ---answer.
Everytime you do 1 revolution (-2pi), you will get another one.