Derivative of sin3(t)\sin^{3}{\left(t \right)}

The calculator will find the derivative of sin3(t)\sin^{3}{\left(t \right)}, with steps shown.

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Your Input

Find ddt(sin3(t))\frac{d}{dt} \left(\sin^{3}{\left(t \right)}\right).

Solution

The function sin3(t)\sin^{3}{\left(t \right)} is the composition f(g(t))f{\left(g{\left(t \right)} \right)} of two functions f(u)=u3f{\left(u \right)} = u^{3} and g(t)=sin(t)g{\left(t \right)} = \sin{\left(t \right)}.

Apply the chain rule ddt(f(g(t)))=ddu(f(u))ddt(g(t))\frac{d}{dt} \left(f{\left(g{\left(t \right)} \right)}\right) = \frac{d}{du} \left(f{\left(u \right)}\right) \frac{d}{dt} \left(g{\left(t \right)}\right):

(ddt(sin3(t)))=(ddu(u3)ddt(sin(t))){\color{red}\left(\frac{d}{dt} \left(\sin^{3}{\left(t \right)}\right)\right)} = {\color{red}\left(\frac{d}{du} \left(u^{3}\right) \frac{d}{dt} \left(\sin{\left(t \right)}\right)\right)}

Apply the power rule ddu(un)=nun1\frac{d}{du} \left(u^{n}\right) = n u^{n - 1} with n=3n = 3:

(ddu(u3))ddt(sin(t))=(3u2)ddt(sin(t)){\color{red}\left(\frac{d}{du} \left(u^{3}\right)\right)} \frac{d}{dt} \left(\sin{\left(t \right)}\right) = {\color{red}\left(3 u^{2}\right)} \frac{d}{dt} \left(\sin{\left(t \right)}\right)

Return to the old variable:

3(u)2ddt(sin(t))=3(sin(t))2ddt(sin(t))3 {\color{red}\left(u\right)}^{2} \frac{d}{dt} \left(\sin{\left(t \right)}\right) = 3 {\color{red}\left(\sin{\left(t \right)}\right)}^{2} \frac{d}{dt} \left(\sin{\left(t \right)}\right)

The derivative of the sine is ddt(sin(t))=cos(t)\frac{d}{dt} \left(\sin{\left(t \right)}\right) = \cos{\left(t \right)}:

3sin2(t)(ddt(sin(t)))=3sin2(t)(cos(t))3 \sin^{2}{\left(t \right)} {\color{red}\left(\frac{d}{dt} \left(\sin{\left(t \right)}\right)\right)} = 3 \sin^{2}{\left(t \right)} {\color{red}\left(\cos{\left(t \right)}\right)}

Thus, ddt(sin3(t))=3sin2(t)cos(t)\frac{d}{dt} \left(\sin^{3}{\left(t \right)}\right) = 3 \sin^{2}{\left(t \right)} \cos{\left(t \right)}.

Answer

ddt(sin3(t))=3sin2(t)cos(t)\frac{d}{dt} \left(\sin^{3}{\left(t \right)}\right) = 3 \sin^{2}{\left(t \right)} \cos{\left(t \right)}A