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September 17, 2014

September 17, 2014

Posted by **Katie** on Monday, March 5, 2012 at 7:12pm.

please help... this is the only one I

didn't understand out of all my homework...

- Trig -
**Steve**, Monday, March 5, 2012 at 11:46pmsin(a+b)sin(a-b)

(sina cosb + cosa sinb)(sinacosb - cosa sinb)

sin^2acos^2b + sinacosasinbcosb - sinacosasinbcosb - cos^2asin^2b)

(1-cos^2a)cos^2b - (1-cos^2b)cos^2a

cos^2b - cos^2acos^2b - cos^2a + cos^2acos^2b

cos^2b - cos^2a

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