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∫sin(x-a)cos(x+b) dx

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Question

`int (sin(x - "a"))/(cos (x + "b"))  "d"x`

Sum
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Solution

Let I = `int (sin(x - "a"))/(cos (x + "b"))  "d"x`

= `int (sin[(x + "b") - ("a" + "b")])/(cos(x + b)  "d"x`

= `int (sin(x + "b")*cos("a" + "b") - cos(x + "b")*sin("a" + "b"))/(cos(x + "b"))  "d"x`

= `int[(sin(x + "b")*cos("a" + "b"))/(cos(x + "b")) - (cos(x + "b")*sin("a" + "b"))/(cos(x + "b"))]  "d"x`

= `int [tan (x + "b")*cos("a" + "b") - sin("a" + "b")]  "d"x`

= `cos("a" + "b") int tan(x + "b")*  "d"x - sin("a" + "b") int "d"x`

∴ I = cos (a + b). log |sec (x + b)| – [sin (a + b)] x + c

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Chapter 2.3: Indefinite Integration - Short Answers I

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