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August 27, 2014

August 27, 2014

Posted by **House** on Friday, October 3, 2008 at 1:16pm.

tan(a) = -1/2

oppsite side = 1: adjacentside = 2

hypotenuse = sqrt(1+4) = sqrt(5)

sin(a) = 1/5

cos(a) = -2/5

tan(b) = -2/3

opposite side = 2 and adjacentside = 3

hypotenuse = sqrt(4+9) = 13

sin(b) = 2/13

cos(b) = -3/13

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

=(-2/5)(-3/13) - (1/5)(2/13)

= 6/65 - 2/65

= 4/65

right?

- Math -
**bobpursley**, Friday, October 3, 2008 at 1:58pmI didn't check all, but you have the technique. You can easily check these on your calculator.

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