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December 17, 2014

December 17, 2014

Posted by **sayan** on Wednesday, April 11, 2012 at 11:56pm.

- maths -
**Steve**, Thursday, April 12, 2012 at 10:36amsin a = 4/5

sin b = -24/25

cos b = -7/25

cos(a+b) = cosa*cosb-sina*sinb

= (-3/5)(-7/25) - (4/5)(-24/25)

= 21/125 + 96/125

= 117/125

now apply the formula for sin(a-b) the same way.

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