Math Problem Statement

Select all true statements about derivatives and critical points based on the mathematical conditions provided.

Solution

Let's analyze the mathematical statements in the uploaded image one by one.

1. На интервале (π2,3π2)\left(\frac{\pi}{2}, \frac{3\pi}{2}\right) найдется точка cc, в которой производная функции y=cosxy = \cos x равна нулю.

  • The derivative of y=cosxy = \cos x is y=sinxy' = -\sin x.
  • For y=0y' = 0, we solve sinx=0-\sin x = 0, which means sinx=0\sin x = 0.
  • Within the interval (π2,3π2)\left(\frac{\pi}{2}, \frac{3\pi}{2}\right), sinx\sin x is never zero because the sine function is negative in this range.

Conclusion: This statement is false.


2. Точка x0=0x_0 = 0 — точка строгого локального минимума функции y=xy = |x|.

  • The function y=xy = |x| is defined as: x, & \text{if } x \geq 0, \\ -x, & \text{if } x < 0. \end{cases}$$
  • At x0=0x_0 = 0, the value of yy is 0, and it is the lowest point of the function. Since x|x| is symmetric and increasing in both directions, x0=0x_0 = 0 is a strict local minimum.

Conclusion: This statement is true.


3. Поскольку функция y=xy = |x| в точке x0=0x_0 = 0 принимает экстремальное значение и имеет конечную производную y(x0)y'(x_0), то y(x0)=0y'(x_0) = 0.

  • At x=0x = 0, y=xy = |x| has a cusp (corner point), meaning the derivative is undefined there. The left-hand derivative is 1-1, and the right-hand derivative is 11. Therefore, y(x0)y'(x_0) does not exist.

Conclusion: This statement is false.


4. На интервале (0,2)(0, 2) найдется точка cc, в которой производная функции y=x3y = x^3 равна y(c)=4y'(c) = -4.

  • The derivative of y=x3y = x^3 is y=3x2y' = 3x^2. To check if y(c)=4y'(c) = -4, solve 3c2=43c^2 = -4. However, c2c^2 cannot be negative, so there is no solution.

Conclusion: This statement is false.


5. На интервале (0,2)(0, 2) найдется точка cc, в которой для производных функций f(x)=x4f(x) = x^4 и g(x)=xg(x) = x выполняется соотношение: f(c)=8g(c)f'(c) = 8g'(c).

  • The derivative of f(x)=x4f(x) = x^4 is f(x)=4x3f'(x) = 4x^3, and the derivative of g(x)=xg(x) = x is g(x)=1g'(x) = 1.
  • For the condition f(c)=8g(c)f'(c) = 8g'(c), we solve 4c3=84c^3 = 8, which gives c3=2c^3 = 2, so c=23c = \sqrt[3]{2}.
  • Since 23(0,2)\sqrt[3]{2} \in (0, 2), such a point exists.

Conclusion: This statement is true.


Final Answer:

The correct statements are:

  • Statement 2: x0=0x_0 = 0 is a strict local minimum of y=xy = |x|.
  • Statement 5: There exists a cc in (0,2)(0, 2) where f(c)=8g(c)f'(c) = 8g'(c) is satisfied.

Would you like a step-by-step solution for any of these?


Here are some related questions to deepen your understanding:

  1. Why does the derivative not exist at sharp points like y=xy = |x| at x=0x = 0?
  2. How do critical points relate to the derivative of trigonometric functions?
  3. Can cubic functions have negative derivative values, and why not in this case?
  4. How do higher-order derivatives influence the geometry of functions?
  5. Could cc exist in other intervals for statement 5, and why?

Tip: Always evaluate intervals carefully when solving derivative equations, as the range of validity might exclude solutions!

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Math Problem Analysis

Mathematical Concepts

Differentiation
Critical points
Intervals of trigonometric and polynomial functions
Local minima and maxima

Formulas

y = cos(x), derivative y' = -sin(x)
y = |x|, piecewise definition
y = x^3, derivative y' = 3x^2
f(x) = x^4 and g(x) = x, derivatives f'(x) = 4x^3 and g'(x) = 1

Theorems

Properties of derivatives
Conditions for extrema
Cusp and sharp point derivatives

Suitable Grade Level

Undergraduate Math (or Advanced High School Calculus)