under what geometrical conditions would
and whats an example of this function for which
We can do it, but it takes a lot of work
and you're expected to be very familiar with Trigonometry.
I'll go through the whole thing in baby-steps . . .
Note that: .
Double-angle identity: .
Half-angle identity: .
Now we must back-substitute.
We have: .
. . and: .
So we have: .