Math Problem Statement

Find the equations of the tangent lines to the curve y = cos(x) at x = -π/2, 0, and π/2. Graph the curve over the interval [-3π/2, 2π] together with its tangent lines. Label the curve and each tangent line.

Solution

The problem in the image asks for the equations of the tangent lines to the curve y=cos(x)y = \cos(x) at several points x=π2,0,andπ2x = -\frac{\pi}{2}, 0, \text{and} \frac{\pi}{2}, and to graph the curve over a specific interval along with its tangent lines.

Let's focus on part of the problem that asks:

"What is the equation of the tangent line to the curve at x=π2x = -\frac{\pi}{2}?"

Steps to solve:

  1. Find the derivative of the function y=cos(x)y = \cos(x). This gives the slope of the tangent line. dydx=sin(x)\frac{dy}{dx} = -\sin(x)

  2. Evaluate the derivative at x=π2x = -\frac{\pi}{2} to get the slope of the tangent line: dydxx=π2=sin(π2)=(1)=1\frac{dy}{dx}\bigg|_{x=-\frac{\pi}{2}} = -\sin\left(-\frac{\pi}{2}\right) = -(-1) = 1 So, the slope of the tangent line is 11.

  3. Find the y-coordinate at x=π2x = -\frac{\pi}{2}: y=cos(π2)=0y = \cos\left(-\frac{\pi}{2}\right) = 0 So, the point of tangency is (π2,0)\left(-\frac{\pi}{2}, 0\right).

  4. Use the point-slope form of the equation of a line: yy1=m(xx1)y - y_1 = m(x - x_1) where m=1m = 1 is the slope, and (x1,y1)=(π2,0)\left(x_1, y_1\right) = \left(-\frac{\pi}{2}, 0\right) is the point of tangency. Substituting the values: y0=1(x(π2))y - 0 = 1\left(x - \left(-\frac{\pi}{2}\right)\right) y=x+π2y = x + \frac{\pi}{2}

Thus, the equation of the tangent line at x=π2x = -\frac{\pi}{2} is: y=x+π2y = x + \frac{\pi}{2}


Would you like more details on graphing the curve and the tangent lines or explanations for the other points?

Here are some related questions for deeper understanding:

  1. How do we determine the slope of a tangent line from the derivative?
  2. What is the significance of evaluating the function at a particular point?
  3. How do you find the equation of a tangent line if the function is more complex?
  4. Can the process be generalized for other trigonometric functions like y=sin(x)y = \sin(x)?
  5. What are the possible uses of tangent lines in applied problems?

Tip: The point-slope form of a line is very useful for quickly finding the equation of a tangent line once the slope is known.

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Math Problem Analysis

Mathematical Concepts

Calculus
Derivatives
Trigonometric Functions

Formulas

Derivative of y = cos(x) is dy/dx = -sin(x)
Point-slope form of a line: y - y1 = m(x - x1)

Theorems

Derivative rules for trigonometric functions
Slope of tangent line theorem

Suitable Grade Level

Grades 11-12