Finding the Derivative of sin(x)cos(x)

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Homework Statement



partial derivative (d/dx) sin(x)cos(x)

Homework Equations



Partial Derivatives, product rule

The Attempt at a Solution



sin(2x) = 2 sin x cos x, therefore y=sin(2x)/2

so y'=cos(2x)*(2/2) = cos (2x)?

Is this correct?
Is there an easier way of directly finding the derivative without using substitution?
 
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I don't see why you would be using partial differentiation with this problem? It is not a product of two variables?

No, that's the quickest method. Use the trig identity to avoid product rule.

Either way, GOOD JOB!
 
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Prove $$\int\limits_0^{\sqrt2/4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx = \frac{\pi^2}{8}.$$ Let $$I = \int\limits_0^{\sqrt 2 / 4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx. \tag{1}$$ The representation integral of ##\arcsin## is $$\arcsin u = \int\limits_{0}^{1} \frac{\mathrm dt}{\sqrt{1-t^2}}, \qquad 0 \leqslant u \leqslant 1.$$ Plugging identity above into ##(1)## with ##u...
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