y = x^4 - 4x^3 - 2 cos (x) + tan (x) question asks to differentiate the following function the answer i believe is 4x^3 - 16x^2 + 2 sin (x) + tan (x) do i have the correct answer?
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Originally Posted by JontyP y = x^4 - 4x^3 - 2 cos (x) + tan (x) question asks to differentiate the following function the answer i believe is 4x^3 - 16x^2 + 2 sin (x) + tan (x) do i have the correct answer? no, the derivative of tan(x) is not tan(x) why do you feel tan(x) should stay the same?
oops i missed out the last bit of the answer! it should look like this 4x^3 - 12x^2 + 2 sin (x) + (1/cos^2(x)) i've changed the -16x^2 to a -12 too
Originally Posted by JontyP oops i missed out the last bit of the answer! it should look like this 4x^3 - 12x^2 + 2 sin (x) + (1/cos2(x)) i've changed the -16x^2 to a -12 too that's correct now. by the way, we can write $\displaystyle \frac 1{\cos^2 x}$ as $\displaystyle \sec^2 x$
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