Hello, I Really Need Help With Trigonometric Identities

**Raiden_11** · January 20th 2008, 06:49 PM

Hello, i need help with trigonometric identities, if anyone can help me, please add me to your msn messenger, my e-mail is falcolneye@hotmail.com, i need someone to help me!!!

THANKYOU!

**Krizalid** · January 20th 2008, 06:56 PM

No, that doesn't make any sense.

Post your problems and show us what you've done.

Make it nice and understandable with math formulae. (See my signature.)

**Raiden_11** · January 20th 2008, 07:03 PM

cos²xcos²y+sin²xsin²y+sin²x+cos²y+sin²ycos²x=1

solve this using reciprocal identities, quotient identities, pythagorean identities

**badgerigar** · January 20th 2008, 07:30 PM

cos²xcos²y+sin²xsin²y+sin²x+cos²y+sin²ycos²x=1

$ cos^2x(cos^2y+sin^2y)+sin^2xsin^2y+sin^2x+cos^2y = 1$
$ cos^2x+sin^2x+sin^2xsin^2y+cos^2y = 1$
$sin^2xsin^2y+cos^2y = 0$
$ (sinxsiny)^2 = -cos^2y$

Since $(sinxsiny)^2 \geq 0$ and $-cos^2y \leq 0$
$ (sinxsiny)^2 = -cos^2y = 0$
$ y = \frac{\pi}{2} +n\pi$
$ x = m\pi$
where n,m are integers.

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Hello, I Really Need Help With Trigonometric Identities

well here's my first problem

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