Preparing for next year 2

**jonoe** · December 12th 2010, 07:23 PM

Hi,

I've asked for a list of questions from a teacher to do over the holidays. I'm struggling to use the text book to help me.

Could someone provide HOW to do these questions, as I just want to get an idea of what I'm getting next year.

Thanks.

3. Evaluate $P=sin6°sin42°sin66°sin78°$

4. Use the formula $tan2x = (2tanx)/(1-tan^2 x)$ to find a surd expression for $tan(pi/8)$

**dwsmith** · December 12th 2010, 07:32 PM

Evaluate how? Just put in the calculator and multiple unless the teacher wants you to use product to sum formulas but those don't go anywhere.

surd expression? What is that?

**jonoe** · December 12th 2010, 07:46 PM

I don't know :S

They got 3 marks next to them.

Getting a holiday tutor soon, but thought i'd try here first.

**mr fantastic** · December 12th 2010, 10:26 PM

Originally Posted by jonoe

[snip]
4. Use the formula $tan2x = (2tanx)/(1-tan^2 x)$ to find a surd expression for $tan(pi/8)$

Substitute x = pi/8 into the given formula. The answer is the positive (why?) solution to $\displaystyle 1 = \frac{2t}{1 - t^2}$ ....

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