Is this correct?Yes, your solution is correct. Good job!

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SUMMARY

The discussion confirms the correctness of the derivative solution for the function 2sin(x)cos(x). The initial attempt at a solution, which resulted in (2cos(x)cos(x)) - (2sin(x)sin(x)), is validated but recommended for simplification to 2cos²(x) - 2sin²(x). This expression is recognized as a trigonometric identity, specifically 2cos(2x), which could have been derived more efficiently by applying the identity 2sin(x)cos(x) = sin(2x) directly.

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1 more derivative problem!

Homework Statement


Find the derivative of...
2sinxcosx
not simplified

The Attempt at a Solution


(2cosxcosx) - (2sinxsinx)

I just want to make sure this is right
 
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yes that is correct..but you should simplify cosxcosx to cos^2x and likewise with the sinxsinx
 
rock.freak667 said:
yes that is correct..but you should simplify cosxcosx to cos^2x and likewise with the sinxsinx

And, when you're done, does that result look like a trig identity you've seen before? Could you have gotten the same result by using a trig identity on 2 sin x cos x first?
 


dy/dx = 2 sin x . -sin x +cos x . cos x= 2 ( cos squared - sin squared)

So yes your correct
 
Last edited:


Which, as dynamicsolo hinted, is the same as 2 cos(2x) and could have been done more simply by recognizing that 2 sin(x) cos(x)= sin(2x).
 

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