Expert: Ahmed Salami - 12/1/2005

Question
How do you simplify the trig function

sin(theta + pi)/ cos(theta - pi)

Answer
Hi Mike,
I'm sorry it took some time.
Well, as it happens on the sin and cos graphs, any movement of pi units forward(+ pi) or backwards(- pi)always changes the sign of the value of the function. You can take a look yourself and find out. Therefore,
sin(theta + pi)= -sin theta
cos(theta - pi)= -cos theta
Simplifying then gives
sin(theta + pi)/ cos(theta - pi) = -sin theta / -cos theta
= tan theta
I hope you get it, you can always get back to me.
Regards.