Some Strategies for Proving Trigonometric Identities
(1) Work with the more complicated side of the identity ﬁrst.
(2) Rewrite both sides of the identity exclusively in terms of sine
(3) Use a Pythagorean identity to make an appropriate
(4) Simplify complex fractions or rewrite fractions sums or
differences with a single denominator.
(5) Use factoring (especially differences of squares).
All of the above are just suggestions or quot;rules of thumb.quot;
Feel free to disregard any or all of the above at any time.
Even and Odd Identities
cos(-x) = cos(x) tan(-x) = -tan(x)
sin(-x) = -sin(x)
The sine and tangent functions are ODD functions.
Cosine is an EVEN function.
Next time in
math class ...
cat attack by ﬂickr user fuffer