- #1
Dethrone
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Homework Statement
In integration, we are allowed to use identities such as [itex]sinx = \sqrt{1-cos^2x}[/itex]. Why does that work, and why doesn't make a difference in integration? Graphing [itex]\sqrt{1-cos^2x}[/itex] is only equal to sinx on certain intervals such as[itex](0, \pi) [/itex]and [itex](2\pi, 3\pi)[/itex]. More correctly, shouldn't we use the absolute value of [itex]\sin\left({x}\right)[/itex]?
[itex]sin^2x = 1 - cos^2x[/itex]
[itex]|sinx| = \sqrt{1 = cos^2x}[/itex]
or defined piecewisely = {[itex]\sin\left({x}\right)[/itex] in regions where it is above the x-axis, and -[itex]\sin\left({x}\right)[/itex] in regions where x is below the x-axis.
Is it possible to even truly isolate "[itex]sin\left({x}\right)[/itex]" from
[itex]sin^2x = 1 - cos^2x[/itex]? It seems as the |[itex]sin\left({x}\right)[/itex]| is the closest we can to isolate it.
Sorry if I may seem confusing, but the concept of absolute value still confuses me.