Asked by Davis

Suppose that 0degrees<theta<180degrees. what is the sign of each of the following?

a) cos theta/2

b)sin(-theta)

Answers

Answered by santosh
cos theta/2 is positive and sin(-theta) is negative
Answered by Davis
How do you know by looking at them?
Answered by Damon
Sketch a graph

If theta is between 0 and 180 then theta/2 is between 0 and 90. Therefore in the first quadrant.
In the first quadrant, all trig functions are positive.

If theta is between 0 and 180 then negative theta is between 180 and 360 in the lower two quadrants, quadrants 3 and 4. In those quadrants y is negative so sin theta is negative.
Answered by Davis
oh okay! I get it now, thanks!:)
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