# Help me solve f(x)=7arctan(2sin(3x)), f′(x)=?

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Based on what I did it should be [42cos3x]/[3-2cos(6x)] but that's wrong.

Based on what I did it should be [42cos3x]/[3-2cos(6x)] but that's wrong.

##### 1 Answer

Feb 17, 2018

#### Explanation:

You'll have to memorize this rule:

Use chain rule to find:

u'=

Plug that and into the rule and remember to multiply by that pesky seven!