Prove and use sin^2(theta)+cos^2(theta)=1 to find trig values with quadrant information.
Determine the signs of sine and cosine when the quadrant is known
Problem
Determine the signs of \(\text{sine}\) and \(\text{cosine}\) in Quadrant \(I\).
Big Picture
What this problem is really about
Trig signs come directly from coordinates on the unit circle: cosine follows the horizontal coordinate and sine follows the vertical coordinate. We’ll locate the quadrant relative to both axes and transfer its coordinate signs to the two functions without swapping their roles.
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