You can put this solution on YOUR website! when cot a = 2/5 and cos b = -3/5 find cos(a+b)
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Angle A could be in Q1 or Q3, not specified.
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Find sin(A) & cos(A):
tan = 1/cot
tan(A) = y/x = 5/2
r = sqrt(5^2+2^2) = sqrt(29)
cos = x/r
cos(A) = 2sqrt(29)/29
sin = sqrt(1 - cos^2)
sin(A) = sqrt(783)/29 = 3sqrt(87)/29
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Find sin(B)
sin = sqrt(1 - cos^2)
sin(B) = 4/5
Here again, B could be in Q2 or Q3, not given.
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cos(A+B) = cos(A)cos(B) - sin(A)sin(B)
= (2sqrt(29)/29)*(-3/5) - (3sqrt(87)/29)*(4/5)
=
