Answer:
First, let's recall some usefull information:
- cot(x) = 1/tg(x) = cos(x)/sin(x)
- tan(x) = sin(x)/cos(x)
We also know that:
- cos(x - pi/2) = sin(x)
- sin(x - pi/2) = -cos(x)
Now we can use those relationships and get:
cot(x - pi/2) = cos(x - pi/2)/sin(x -pi/2) = sin(x)/-cos(x) = -tan(x)
So we have verified the identity, and explained step by step why the identity is true.
