Find the derivatives of the following trigonometric functions: 1) f(x) = sin(3x) 2) f(x) = cos(5x) 3) f(x) = cot(8x) 4) g(x) = sec(8x) 5) P(x) = tan(2x) 6) h(x) = cosec(6x)

Question image

Understand the Problem

The question asks to find the derivatives of trigonometric functions. The image provides a list of trigonometric functions and their derivatives. Therefore, this is a math question.

Answer

All given derivatives are incorrect.
Answer for screen readers
  1. Incorrect. The derivative should be $3cos(3x)$
  2. Incorrect. The derivative should be $-5sin(5x)$
  3. Incorrect. The derivative should be $-8cosec^2(8x)$
  4. Incorrect. The derivative should be $8sec(8x)tan(8x)$
  5. Incorrect. The derivative should be $2sec^2(2x)$
  6. Incorrect. The derivative should be $-6cosec(6x)cot(6x)$

Steps to Solve

  1. Derivative of $sin(ax)$

The derivative of $sin(ax)$ is $a \cdot cos(ax)$. Therefore, the derivative of $f(x) = sin(3x)$ is $f'(x) = 3cos(3x)$. The provided answer is $cos(3x)$ - missing the factor of 3. This is incorrect.

  1. Derivative of $cos(ax)$

The derivative of $cos(ax)$ is $-a \cdot sin(ax)$. Therefore, the derivative of $f(x) = cos(5x)$ is $f'(x) = -5sin(5x)$. The provided answer is $-sin(5x)$ - missing the factor of 5. This is incorrect.

  1. Derivative of $cot(ax)$

The derivative of $cot(ax)$ is $-a \cdot cosec^2(ax)$. Thus, the derivative of $f(x) = cot(8x)$ is $f'(x) = -8cosec^2(8x)$. The provided answer is $-cosec^2(8x)$ - missing the factor of 8. This is incorrect.

  1. Derivative of $sec(ax)$

The derivative of $sec(ax)$ is $a \cdot sec(ax)tan(ax)$. Therefore, the derivative of $g(x) = sec(8x)$ is $g'(x) = 8sec(8x)tan(8x)$. The provided answer, $\frac{sec(x)8x}{tan(x)}$, is incorrect. It should be $8sec(8x)tan(8x)$.

  1. Derivative of $tan(ax)$

The derivative of $tan(ax)$ is $a \cdot sec^2(ax)$. Therefore, the derivative of $p(x) = tan(2x)$ is $p'(x) = 2sec^2(2x)$. The provided answer $\frac{1}{1+x^2}2x$ which simplifies to $\frac{2x}{1+x^2}$ which is incorrect. It looks like someone was trying to apply the derivative for $arctan(x)$ mistakenly.

  1. Derivative of $cosec(ax)$

The derivative of $cosec(ax)$ is $-a \cdot cosec(ax)cot(ax)$. The derivative shown is incomplete lacking both the factor of 6, as well as the $cot(ax)$ term.

  1. Incorrect. The derivative should be $3cos(3x)$
  2. Incorrect. The derivative should be $-5sin(5x)$
  3. Incorrect. The derivative should be $-8cosec^2(8x)$
  4. Incorrect. The derivative should be $8sec(8x)tan(8x)$
  5. Incorrect. The derivative should be $2sec^2(2x)$
  6. Incorrect. The derivative should be $-6cosec(6x)cot(6x)$

More Information

All of the provided derivatives are incorrect, some missing a multiplicative constant obtained via the chain rule, or a trigonometric term.

Tips

  • Forgetting to apply the chain rule when differentiating trigonometric functions with a composite argument (e.g., $\sin(3x)$). This leads to missing the constant factor.
  • Incorrectly recalling the derivatives of trigonometric functions.
  • Confusing derivatives of different trigonometric functions like $\tan(x)$ and $\arctan(x)$.

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