Here's the question you clicked on:
acbarnes3
Verify tan(x + pi/2) = -cotx
tan ( x+ pi/2) = tan ( 90 + x) since the angle is in the second quadrant .where tan is negative. thus the negative sign. and the angle from the horizontal is 180-(90+x) =90-x..hence it changes to cot therefore tan(90=x) = - cotx
To cut out on the theory, mathematically you can prove it like this : tan(pi/2 +x) = tan(pi/2 - (-x)) = cot(-x) = -cotx
i think u need some other method, the very basic method ? |dw:1359120108418:dw|
just put b=Pi/2 u will get -1/tanc =-cotx
tan(x + pi/2) = -cotx it another way of saying cot x flipped along x axis and shifted pi/2 to right or left. I think.