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Derivative of x4cos⁡(x)\frac{x^{4}}{\cos\left(x\right)}

The derivative of x4cos⁡(x)\frac{x^{4}}{\cos\left(x\right)} is 4x3cos⁡(x)−x4−sin⁡(x)cos⁡(x)2\frac{4 x^{3} \cos\left(x\right) - x^{4} -\sin\left(x\right)}{\cos\left(x\right)^{2}}.

f(x) =
ddx[x4cos⁡(x)]=4x3cos⁡(x)−x4−sin⁡(x)cos⁡(x)2\frac{d}{dx}\left[\frac{x^{4}}{\cos\left(x\right)}\right] = \frac{4 x^{3} \cos\left(x\right) - x^{4} -\sin\left(x\right)}{\cos\left(x\right)^{2}}

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Graph of f(x) = x^4 / cos(x) and its derivative-3-2-1123-100-5050100slope 10.29f(x)f'(x)tangent at x = 1
Graph of f(x) = x^4 / cos(x) and its derivative. The dashed line is the tangent at x = 1; its slope is f'(1) = 10.286.

How to work it out

  1. 1

    We differentiate f(x)=x4cos⁡(x)f(x) = \frac{x^{4}}{\cos\left(x\right)} with respect to x. The rule that applies is the quotient rule.

    f(x)=x4cos⁡(x)f(x) = \frac{x^{4}}{\cos\left(x\right)}
  2. 2

    Quotient rule: (uv)′=u′v−uv′v2\left(\frac{u}{v}\right)' = \frac{u'v - uv'}{v^{2}}. Let u=x4u = x^{4} and v=cos⁡(x)v = \cos\left(x\right).

    u=x4,v=cos⁡(x)u = x^{4},\quad v = \cos\left(x\right)
  3. 3

    Differentiate each piece:

    u′=4x3,v′=−sin⁡(x)u' = 4 x^{3},\quad v' = -\sin\left(x\right)
  4. 4

    Put them in the rule:

    f′(x)=(4x3)(cos⁡(x))−(x4)(−sin⁡(x))(cos⁡(x))2f'(x) = \frac{\left(4 x^{3}\right)\left(\cos\left(x\right)\right) - \left(x^{4}\right)\left(-\sin\left(x\right)\right)}{\left(\cos\left(x\right)\right)^{2}}
  5. 5

    Simplify:

    f′(x)=4x3cos⁡(x)−x4−sin⁡(x)cos⁡(x)2f'(x) = \frac{4 x^{3} \cos\left(x\right) - x^{4} -\sin\left(x\right)}{\cos\left(x\right)^{2}}
  6. 6

    Differentiating once more gives the second derivative, which tells you about curvature:

    f′′(x)=(12x2cos⁡(x)+4x3−sin⁡(x)−(4x3−sin⁡(x)+x4−cos⁡(x)))cos⁡(x)2−(4x3cos⁡(x)−x4−sin⁡(x))2cos⁡(x)−sin⁡(x)(cos⁡(x)2)2f''(x) = \frac{\left(12 x^{2} \cos\left(x\right) + 4 x^{3} -\sin\left(x\right) - \left(4 x^{3} -\sin\left(x\right) + x^{4} -\cos\left(x\right)\right)\right) \cos\left(x\right)^{2} - \left(4 x^{3} \cos\left(x\right) - x^{4} -\sin\left(x\right)\right) 2 \cos\left(x\right) -\sin\left(x\right)}{\left(\cos\left(x\right)^{2}\right)^{2}}
LaTeX source of the formulas on this page
\[ \frac{d}{dx}\left[\frac{x^{4}}{\cos\left(x\right)}\right] = \frac{4 x^{3} \cos\left(x\right) - x^{4} -\sin\left(x\right)}{\cos\left(x\right)^{2}} \]
\[ f(x) = \frac{x^{4}}{\cos\left(x\right)} \]
\[ u = x^{4},\quad v = \cos\left(x\right) \]
\[ u' = 4 x^{3},\quad v' = -\sin\left(x\right) \]
\[ f'(x) = \frac{\left(4 x^{3}\right)\left(\cos\left(x\right)\right) - \left(x^{4}\right)\left(-\sin\left(x\right)\right)}{\left(\cos\left(x\right)\right)^{2}} \]
\[ f'(x) = \frac{4 x^{3} \cos\left(x\right) - x^{4} -\sin\left(x\right)}{\cos\left(x\right)^{2}} \]
\[ f''(x) = \frac{\left(12 x^{2} \cos\left(x\right) + 4 x^{3} -\sin\left(x\right) - \left(4 x^{3} -\sin\left(x\right) + x^{4} -\cos\left(x\right)\right)\right) \cos\left(x\right)^{2} - \left(4 x^{3} \cos\left(x\right) - x^{4} -\sin\left(x\right)\right) 2 \cos\left(x\right) -\sin\left(x\right)}{\left(\cos\left(x\right)^{2}\right)^{2}} \]

Values of f and f' for x4x^{4} / cos(x)

xf(x)f'(x)
-2-38.447967-7.1144066
-11.8508157-10.285738
0.50.071218370.60865374
11.850815710.285738
2-38.4479677.1144066
3-81.818802-97.428749

Questions

What is the derivative of x4x^{4} / cos(x)?

The derivative of x4cos⁡(x)\frac{x^{4}}{\cos\left(x\right)} is 4x3cos⁡(x)−x4−sin⁡(x)cos⁡(x)2\frac{4 x^{3} \cos\left(x\right) - x^{4} -\sin\left(x\right)}{\cos\left(x\right)^{2}}.

What is the second derivative of x4x^{4} / cos(x)?

((12 * x2x^{2} * cos(x) + 4 * x3x^{3} * -sin(x) - (4 * x3x^{3} * -sin(x) + x4x^{4} * -cos(x))) * cos(x)^2 - (4 * x3x^{3} * cos(x) - x4x^{4} * -sin(x)) * 2cos(x) * -sin(x)) / (cos(x)^2)^2.

Which rule do you use for x4x^{4} / cos(x)?

The quotient rule.

What is the slope of x4x^{4} / cos(x) at x = 1?

10.285738.

Related derivatives

    Derivative of x^4 / cos(x): (4 * x^3 * cos(x) - x^4 * -sin(x)) / cos(x)^2 (with steps) | WordGPT