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I've looked at various online integral calculators including Wolfram Alpha and I can't find anything for absolute values when it comes to sine and cosine waves.

For example: If I have $y=|\sin(3x)+\sin(7x)|$, and I want to find the integral of it for $x=0$ to $2$, how would I do that?

Kenta S
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Alice T
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2 Answers2

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Maybe consider what the absolute value function does. How could you approach this?

You know from a fundamental level that integrating can be thought of taking the area of something. How an absolute value affect this operation?

Graphing y and |y| may also give you some insight on what the absolute value operation is doing.

Hint: You probably will need to solve f(x) = 0

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$\textbf{Hint:}$ $5$ is halfway between $3$ and $7$ which means we can use the expression

$$|\sin(5x-2x)+\sin(5x+2x)| = |2\sin 5x \cos 2x|$$

by sine angle addition formulas.

Ninad Munshi
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