Monday

September 15, 2014

September 15, 2014

Posted by **Alice** on Saturday, February 21, 2009 at 4:23pm.

work on one side only...so i worked on the right

=(sinx-siny)(sinx+siny) does that equal

sin(x-y)sin(x+y)??? help!

- Trig -
**drwls**, Saturday, February 21, 2009 at 5:50pmUse the formulas for sin (A-B) and sin (A+B)

The left side is

(sinx cos y - siny cosx)(sinx cosy + siny cosx)

= sin^2x cos^2y - sin^2y cos^2 x

=(1 - cos^2x)(cos^2y)-sin^2y cos^2x

= cos^2y -cos^2y cos^2x - sin^2y cos^2x

= cos^2y -cos^2x

= 1-sin^2y -1 + sin^2x

= sin^2x - sin^2y

**Answer this Question**

**Related Questions**

trig!! - Sin(X-y)sin(x+y)=sin^2 x - sin^2 y work on one side only...so i worked ...

trig - Okay, I've been getting some of these, but I can't seem to verify this ...

TRIG! - Posted by hayden on Monday, February 23, 2009 at 4:05pm. sin^6 x + cos^6...

calculus - Could someone check my reasoning? thanx Find the derivative of the ...

Precalculus/Trig - I can't seem to prove these trig identities and would really ...

Trig - Simplify sin x cos^2x-sinx Here's my book's explanation which I don't ...

Math help again - cos(3π/4+x) + sin (3π/4 -x) = 0 = cos(3π/4)cosx...

pre calc trig check my work please - sin x + cos x -------------- = ? sin x sin ...

Math (trigonometric identities) - I was given 21 questions for homework and I ...

tigonometry - expres the following as sums and differences of sines or cosines ...