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PLZ PLZ HELP!!!!!! The expression cos(A+pi) - sin(A + pi) can be simplified to
a) sin(A) - cos(A)
b) sin(A) + cos(A)
c) cos(A)- sin(A)
d) -sin(A) - cos(A)



Answer :

olemakpadu
Sin(A+B) = SinACosB + CosASinB
Cos(A+B) = CosACosB - SinASinB

Note pi is taken as pi radians = 180 degrees.    Cospi = Cos180 = -1.
                                                                                       Sinpi  = Sin 180 = 0

Cos(A+pi) = CosACospi - SinASinpi =  (CosA) * (-1) - (SinA) *(0) = -CosA.
Sin(A+pi) = SinACospi + CosASinpi  =  (SinA)* (-1) + (CosA) * (0) = -SinA.

Cos(A+pi) - Sin(A+pi) = -CosA - -SinA = -CosA + SinA = SinA  - CosA.

Answer = (a).

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