Posted by **Max** on Thursday, March 28, 2013 at 1:46pm.

Simplify (sin^2)*(67.5deg) - (cos^2)*(67.5deg) and then evaluate exactly.

- Trig -
**Steve**, Thursday, March 28, 2013 at 1:49pm
well, cos 2x = cos^2 x - sin^2 x, so what do you think?

If you end up with 1/√2 you are correct.

- Trig -
**Max**, Thursday, March 28, 2013 at 3:13pm
How exactly do you get there though? I tried to follow a similar homework problem and got:

= (cos^2)*(67.5deg) - (sin^2)*(67.5deg)

= cos(2*67.5deg)

= cos135deg

= -√2/2

- Trig -
**Steve**, Thursday, March 28, 2013 at 3:20pm
note that the problem was

sin^2(67.5)-cos^2(67.5)

= -cos(135)

my hint was not intended to make you forget what was originally asked. :-)

And, I know lots of folks hate roots in the denominator, but I see no reason why √2/2 is better than 1/√2. Just mt preference

- Trig -
**Max**, Thursday, March 28, 2013 at 5:20pm
Thank you very much!

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