Double angle trigonometry....NEED HELP PLEASE!!

Hi guys, I am new to this forum and really need some help.

I have been trying to complete a maths assignment for my college work but have come across a question that I am totally stuck on and my lecturer wont help me!!

Can someone help me please?!?!

The question is:

Give the exact value for the following:

2tan75°

______

1-tanē75°

If someone could please please help me..

I need to know the working and each step that was taken to get to the final answer....

Please explain :)

Thanks :)

Re: Double angle trigonometry....NEED HELP PLEASE!!

If you write the formula out using sine and cosine equivalents you get:

Now simplify - multiply numerator and denominator by :

Now the numerator is in the form of the identity , and the denominator is like . Here x = 75, so the original equation is equivalent to:

You can know determine an exact value for this, since you know the values for both and .

Re: Double angle trigonometry

Re: Double angle trigonometry

An alternative method is to use a compound angle formula, since 75 = 30 + 45.

Re: Double angle trigonometry

I really have no idea how to use compound formulas....could you run through it please?

Re: Double angle trigonometry

Re: Double angle trigonometry

Re: Double angle trigonometry

I think you mean .

Re: Double angle trigonometry

Quote:

Originally Posted by

**Prove It** I think you mean

.

Yes - thanks for catching my error!