Math Problem Statement

find the tangent to y = cos x at x = pi/2

Solution

To find the equation of the tangent line to the curve y=cos(x)y = \cos(x) at the point x=π2x = \frac{\pi}{2}, follow these steps:

Step 1: Find the slope of the tangent line

The slope of the tangent line is given by the derivative of the function y=cos(x)y = \cos(x).

y=ddx(cos(x))=sin(x)y' = \frac{d}{dx} \left( \cos(x) \right) = -\sin(x)

Now, evaluate the derivative at x=π2x = \frac{\pi}{2}:

y(π2)=sin(π2)=1y'\left( \frac{\pi}{2} \right) = -\sin\left( \frac{\pi}{2} \right) = -1

So, the slope of the tangent line at x=π2x = \frac{\pi}{2} is 1-1.

Step 2: Find the point of tangency

We already know that x=π2x = \frac{\pi}{2}. To find the corresponding yy-value:

y=cos(π2)=0y = \cos\left( \frac{\pi}{2} \right) = 0

Thus, the point of tangency is (π2,0)\left( \frac{\pi}{2}, 0 \right).

Step 3: Use the point-slope form to find the equation of the tangent line

The point-slope form of a line is:

yy1=m(xx1)y - y_1 = m(x - x_1)

Substitute the slope m=1m = -1 and the point (π2,0)\left( \frac{\pi}{2}, 0 \right):

y0=1(xπ2)y - 0 = -1 \left( x - \frac{\pi}{2} \right)

Simplify the equation:

y=x+π2y = -x + \frac{\pi}{2}

Final Answer:

The equation of the tangent line to the curve y=cos(x)y = \cos(x) at x=π2x = \frac{\pi}{2} is:

y=x+π2y = -x + \frac{\pi}{2}

Would you like more details or have any questions?

Here are 5 related questions:

  1. How would you find the tangent to y=sin(x)y = \sin(x) at x=0x = 0?
  2. Can you find the tangent to y=cos(x)y = \cos(x) at x=0x = 0?
  3. What is the normal line equation at x=π2x = \frac{\pi}{2}?
  4. How does the slope of the tangent change as xx approaches 0 from x=π2x = \frac{\pi}{2}?
  5. How would you find the tangent to a parametric curve at a given point?

Tip: When finding tangents, always differentiate first to obtain the slope at the desired point.

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Math Problem Analysis

Mathematical Concepts

Differentiation
Trigonometry
Tangent Lines

Formulas

y = cos(x)
y' = -sin(x)
Point-slope form: y - y1 = m(x - x1)

Theorems

Derivative of Trigonometric Functions

Suitable Grade Level

Grades 10-12