how do you use the sum-to-product formula to write a product as a sum: 4sin pi/3 cos 5pi/6
S ShanikaC New member Joined Apr 20, 2006 Messages 7 Apr 20, 2006 #1 how do you use the sum-to-product formula to write a product as a sum: 4sin pi/3 cos 5pi/6
skeeter Elite Member Joined Dec 15, 2005 Messages 3,216 Apr 20, 2006 #2 sin(A)cos(B) = (1/2)sin(A+B) + (1/2)sin(A-B) 4sin(pi/3)cos(5pi/6) = 2sin(pi/3 + 5pi/6) + 2sin(pi/3 - 5pi/6) = 2sin(7pi/6) + 2sin(-pi/2) = 2(-1/2) + 2(-1) = -3
sin(A)cos(B) = (1/2)sin(A+B) + (1/2)sin(A-B) 4sin(pi/3)cos(5pi/6) = 2sin(pi/3 + 5pi/6) + 2sin(pi/3 - 5pi/6) = 2sin(7pi/6) + 2sin(-pi/2) = 2(-1/2) + 2(-1) = -3
