A bit of trivia about language:
Notice the "CO" in the word "CO-function". It has to
do with COMPLEMENT.
The "CO" in the word "CO-SINE" means "COMPLEMENT'S".
So the CO-SINE is the COMPLEMENT'S SINE.
Similarly,
The CO-TANGENT is the COMPLEMENT'S TANGENT.
and
The CO-SECANT is the COMPLEMENT'S SECANT.
So is its complement's cosine.
Its complement is
So the cofunction that's equal to is
.
IOW, and are exactly the same
thing! Also and are exactly
the same thing. You can easily convince yourself of that with
a calculator (placed in RADIAN mode).
-----
Here's why:
Think of a right triangle, where the two acute angles are complements
of each other. The side that is opposite one angle is adjacent the
other. That explains cofunction. The key is the "CO".
Edwin
