Question...

For the Half-Angle Problems:

http://i10.photobucket.com/albums/a1...CoOkIe/COS.gif

how do you know if the answer is positve or negative...

(i circled it in RED)

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- May 7th 2006, 02:52 PMCONFUSED_ONEOne Half-Angle Queston
Question...

For the Half-Angle Problems:

http://i10.photobucket.com/albums/a1...CoOkIe/COS.gif

how do you know if the answer is positve or negative...

(i circled it in RED) - May 7th 2006, 03:01 PMThePerfectHackerQuote:

Originally Posted by**CONFUSED_ONE**

NOT $\displaystyle a$ but $\displaystyle \frac{a}{2}$.

If $\displaystyle \frac{a}{2}$ is in the first or second quadrant then you use positive, otherwise use the negative.

Your question, is a classic mistake which I seen many people make, hopefully you will not make it. - May 7th 2006, 03:08 PMCONFUSED_ONE
for example, what if a=4/5. so it'll be (4/5)/2 and that'll turn out to be 2/5. how do i know if 2/5 is in the first or second quadrant?

- May 7th 2006, 03:14 PMThePerfectHackerQuote:

Originally Posted by**CONFUSED_ONE**

The first and second quadrant span $\displaystyle 0^o\leq x\leq 180^o$

Or in Radians, $\displaystyle 0\leq x\leq \pi$

Since,

$\displaystyle 0\leq .4\leq 3.14$ it is in the first and second quadrants.

In fact it is in first quadrant because it spans,

$\displaystyle 0\leq x\leq \frac{\pi}{2}\approx 1.57$