Evaluate cosθ when θ=π2.

Question

Cosθ=

Answer 1

I'm not entirely sure if π2 means 2π or if it means π/2, so I will answer for both.

One way we can solve this would be to convert our radians into degrees first.

We can convert radians into degrees by multiplying our radians by 180/π:

2π * 180/π = (2*180*π)/π = 360π/π = 360^o

π/2 * 180/π = (π*180)/(2*π) = 180π/2π = 180/2 = 90^o

So now that we have them in degrees instead of radians, we have

cos(360) and cos(90)

And we know that cos(360) = 1 and cos(90) = 0

These values should be easy to memorize from the unit circle, or simply plug into a calculator if you are allowed one.