Difficult Trig Problem Practice

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This page is for more difficult Trig problems


2cos A cos B=cos(A+B) + cos(A-B)
2sin A sin B= -cos(A+B) + cos(A-B)
2sin A cos B =sin(A+B) + sin(A-B)
2cos A sin B=sin(A+B) - sin(A-B)

cos(a) cos(b) = 1/2 [cos(a + b) + cos(a - b)]
sin(a) sin(b) = 1/2 [cos(a - b) - cos(a + b)]
sin(a) cos(b) = 1/2 [sin(a + b) + sin(a - b)]
cos(a) sin(b) + 1/2 [sin(a + b) - sin(a - b)]

Addition and Subtraction

cosx +cosy= 2cos1/2(x+y)cos1/2(x-y)
cosx -cosy= -2sin1/2(x+y)sin1/2(x-y)
sinx +siny= 2sin1/2(x+y)cos1/2(x-y)
sinx -siny= 2cos1/2(x+y)sin1/2(x-y)

Some Videos:

Try this link to a clear explanation of Sum and Product formulas: Basic Examples Using Sum-to-Product and Product-to-Sum Formulas