Suppose θ is in the interval (180°, 225°). Find the sign of each function value.

a) Cos(2θ)
b) tan(θ-90°)
c) sin(θ/2)

Question

Suppose θ is in the interval (180°, 225°).  Find the sign of each function value.

a) Cos(2θ)
b) tan(θ-90°)
c) sin(θ/2)

dumbcow · Answer

a) 2A puts you in 1st quadrant --> cos(2A) is positive

b) A-90 puts you in 2nd quadrant --> tan(A-90) is negative

c) A/2 puts you in 2nd quadrant --> sin(A/2) is positive

anonymous · Answer

How do you get to that?  Is there any mathmatics behind it that will help me associate it so I can repeat this?

anonymous · Answer

this (rough) diagram should help\
|dw:1328624954731:dw|