# Precalculus : Trigonometric Identities

## Example Questions

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### Example Question #61 : Trigonometric Identities

Given that:

, what is the value of  in function of ?

Explanation:

We know by definition that:

We also have by trigonometric identities:

Thus :

Now we have:

This gives us:

### Example Question #21 : Double And Half Angle Identities

Given that:

Compute

in function of .

Explanation:

We will use the following formulas for calculating the tangent:

We have then:

This gives us :

Simplifying a bit we get :

Writing

We now have :

Using the fact that , we have finally:

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