To determine the value of the sum, we'll create matching
functions in the given sum.
Since sin pi/4 = (sqrt2)/2,
we'll substitute the value (sqrt2)/2 by the equivalent function of the angle
pi/4.
We'll transform the sum into a
product.
sin x + sin pi/4 = sin x +
(sqrt2)/2
sin x + sin pi/4 = 2sin [(x+pi/4)/2]*cos[
(x-pi/4)/2]
sin x + sin pi/4 = 2 sin [(x/2 + pi/8)]*cos[
(x/2 - pi/8)]
We'll use the half angle
identity:
sin [(x+pi/4)/2] = sqrt[2-(sqrt2)*(cos x-sin
x)]/2
cos[ (x-pi/4)/2] = sqrt[2+(sqrt2)*(cos x+sin
x)]/2
sin x + sin pi/4 =
sqrt{[2-(sqrt2)*(cos x-sin x)]*[2+(sqrt2)*(cos x+sin
x)]}/2
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