"Is it that sine is positive in first and second quadrants, while cos/tan are positive in the first and the fourth? "
The answer is yes whether it is related to the evaluation of composition of functions or not.
Can you post an example to clarify the context of the first question?
How's the rule go on evaluating compositions of functions? Is it that sine is positive in first and second quadrants, while cos/tan are positive in the first and the fourth?
1 answer