Question

If sin Θ = 21/29, use the Pythagorean Identity to find cos Θ. A. cos Θ = ± 8 over 29 B. cos Θ = ± 21 over 20 C. cos Θ = ± 29 over 20 D. cos Θ = ± 20 over 29

Answer 1

The answer is D

Explanation:

Answer 2

If If sin Θ = 21/29, then the y-component should be equal to 21 and the hypotenuse is equal to 29. In this case, using the pythgorean theorem, the x-component is obtained from (29^2-21^2)^1/2 equal to 20. Hence cos Θ should be +/-20/29. This has +/- because positive sine  can be  in quadrant II where cosine value is negative