how to do solve this question?

Question

I forgot how to do this type of question, and no longer have a high school textbook to look it up. The only thing I remember is CAST.

cos(116) = ?

please explain the process.

also how do i find co-terminal angles (in radians)? (add and subract 2pi)

what about when its Sin or Tan?

Answer 1

Remember ASTC All Students Take Chances. This says all three are positive in the 1st quadrant, the sine is positive in the 2nd quadrant, the tangent is positive in the 3rd quadrant, and the cosine is positive in the 4t quadrant.

Since 116 degrees lies in the 2nd quadrant, the cosine is going to be negative. The angle is measured from the terminal side to the x-axis which in this case is 180 - 116 = 64 degrees. So the answer is -cos 64 = - .43837.

Answer 2

cosA = -cos(180-A)

hope that helps LOL