# Preparing for next year 2

• December 12th 2010, 07:23 PM
jonoe
Preparing for next year 2
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 $tan(pi/8)$
• December 12th 2010, 07:32 PM
dwsmith
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?
• December 12th 2010, 07:46 PM
jonoe
I don't know :S

They got 3 marks next to them.

Getting a holiday tutor soon, but thought i'd try here first.
• December 12th 2010, 10:26 PM
mr fantastic
Quote:

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 $\displaystyle 1 = \frac{2t}{1 - t^2}$ ....