How do you simplify #csc θsec θ - cot θ#?

1 Answer
Nov 12, 2015

#tan theta#

Explanation:

Lets start by using some trig identities to put the original statement into terms of #sin# and #cos#. Substituting the trig identities for #sec#, #csc#, and #cot# the expression becomes;

#1/sin theta 1/cos theta - cos theta/sin theta#

At this point it would be helpful to have a common denominator. We can do that by multiplying the top and bottom of the second term by #cos theta#.

#1/sin theta 1/cos theta - cos theta/sin theta cos theta/ cos theta#

Now we can combine the numerators over #sin theta cos theta#.

#(1 - cos^2 theta)/(sin theta cos theta)#

We can use the Pythagorean theorem to simplify the numerator. The Pythagorean theorem states that;

#sin^2 theta + cos^2 theta = 1#

Rearranging the terms we get;

#sin^2 theta = 1-cos^2 theta#

Now we can make the substitution for the numerator.

#sin^2 theta/(sin theta cos theta)#

The #sin theta# terms cancel, leaving;

#sin theta/ cos theta#

Which is the definition of #tan#.

#tan theta#