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Prove that
Solution:
Consider the given equation above
In proving the trigonometric functions, the first thing that you have to do is to choose the more complicated side of the equation and then simplify and compare with the other side of the equation if they are equal or not.
In this case, the left side of the equation is more complicated and we have to simplify it as follows
The numerator is the sum of cubes. We can use the principles of Algebra in factoring the numerator as follows
but
then the above equation becomes
Therefore,
