Math Problem Statement

Given f(x) = 4tan(x), write the equation of the line tangent to y = f(x) when x = π/4.

Solution

The problem from your screenshot is asking for the equation of the tangent line to the function f(x)=4tan(x)f(x) = 4 \tan(x) at x=π4x = \frac{\pi}{4}.

Steps to solve:

  1. Find the derivative of f(x)=4tan(x)f(x) = 4 \tan(x), which gives us the slope of the tangent line at any point xx.

f(x)=4sec2(x)f'(x) = 4 \sec^2(x)

  1. Evaluate the derivative at x=π4x = \frac{\pi}{4} to find the slope of the tangent line at this specific point.

f(π4)=4sec2(π4)f'\left(\frac{\pi}{4}\right) = 4 \sec^2\left(\frac{\pi}{4}\right)

Since sec(π4)=2\sec\left(\frac{\pi}{4}\right) = \sqrt{2}, we have:

f(π4)=4×(2)2=4×2=8f'\left(\frac{\pi}{4}\right) = 4 \times \left(\sqrt{2}\right)^2 = 4 \times 2 = 8

So, the slope of the tangent line is 8.

  1. Find the point on the curve at x=π4x = \frac{\pi}{4}:

f(π4)=4tan(π4)=4×1=4f\left(\frac{\pi}{4}\right) = 4 \tan\left(\frac{\pi}{4}\right) = 4 \times 1 = 4

So, the point is (π4,4)\left(\frac{\pi}{4}, 4\right).

  1. Use the point-slope form of a line:

The equation of the tangent line is given by:

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

Where m=8m = 8, (x1,y1)=(π4,4)(x_1, y_1) = \left(\frac{\pi}{4}, 4\right).

y4=8(xπ4)y - 4 = 8 \left( x - \frac{\pi}{4} \right)

Simplifying:

y=8x2π+4y = 8x - 2\pi + 4

So, the equation of the tangent line is:

y=8x2π+4y = 8x - 2\pi + 4

Would you like further details or clarifications on this?

Here are some related questions for further practice:

  1. What is the equation of the tangent line to f(x)=sin(x)f(x) = \sin(x) at x=π6x = \frac{\pi}{6}?
  2. How do you find the derivative of f(x)=tan(x)f(x) = \tan(x)?
  3. What is the significance of the tangent line in the context of a graph of a function?
  4. How would the tangent line change if f(x)=5tan(x)f(x) = 5\tan(x) instead?
  5. Can you describe what happens to the tangent line as xx approaches π\pi?

Tip: Always remember that the tangent line at a given point has the same slope as the derivative of the function at that point.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Derivatives
Tangent Lines

Formulas

f(x) = 4tan(x)
f'(x) = 4sec^2(x)
Point-slope form: y - y₁ = m(x - x₁)

Theorems

Derivative of the tangent function: d/dx[tan(x)] = sec²(x)
Point-slope form for tangent lines

Suitable Grade Level

Grades 11-12