First we look at the double-angle identity of cos2x.
We know that:
cos2x = cos^2x - sin^2x
cos2x = [1-sin^2x] - sin^2x.............. (From sin^2x + cos^2x = 1, cos^2x = 1 - sin^2x)
Therefore:
cos2x = 1 - 2sin^2x
2sin^2x = 1 - cos2x
sin^2x = 1/2(1-cos2x)
sin^2x = 1/2 - cos2x/2
And intergrating, we get:
x/2 - sin2x/4 + c...................(Integral of cos2x = 1/2sin2x; and c is a constant)
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Answer 1 Put simply, sine squared is sinX x sinX. However, sine is a function, so the real question must be 'what is sinx squared' or 'what is sin squared x': 'Sin(x) squared' would be sin(x^2), i.e. the 'x' is squared before performing the function sin. 'Sin squared x' would be sin^2(x) i.e. sin squared times sin squared: sin(x) x sin(x). This can also be written as (sinx)^2 but means exactly the same. Answer 2 Sine squared is sin^2(x). If the power was placed like this sin(x)^2, then the X is what is being squared. If it's sin^2(x) it's telling you they want sin(x) times sin(x).
The integral of x cos(x) dx is cos(x) + x sin(x) + C
arctan(x)
The integral of cot(x)dx is ln|sin(x)| + C
∫ cot(x) dx is written as: ∫ cos(x) / sin(x) dx Let u = sin(x). Then, du = cos(x) dx, giving us: ∫ 1/u du So the integral of 1/u is ln|u|. So the answer is ln|sin(x)| + c