Math Problem Statement

How would the area change if the interval was [0,π][0,π]?

Solution

If the interval is extended to [0,π][0, \pi], we need to find the area of the region enclosed by the curves y=sin(x)y = \sin(x) and y=cos(x)y = \cos(x) over this interval.

Step 1: Determine the Points of Intersection

As before, sin(x)=cos(x)\sin(x) = \cos(x) at x=π4x = \frac{\pi}{4}. Over the interval [0,π][0, \pi], the curves intersect again at x=5π4x = \frac{5\pi}{4}, but we focus only on the region within [0,π][0, \pi].

Step 2: Set Up the Integral

We now split the interval into two parts:

  1. From x=0x = 0 to x=π4x = \frac{\pi}{4}, where cos(x)\cos(x) is above sin(x)\sin(x).
  2. From x=π4x = \frac{\pi}{4} to x=π2x = \frac{\pi}{2}, where sin(x)\sin(x) is above cos(x)\cos(x).
  3. From x=π2x = \frac{\pi}{2} to x=πx = \pi, where sin(x)\sin(x) is above cos(x)\cos(x).

Step 3: Compute the Integrals

For x[0,π4]x \in [0, \frac{\pi}{4}]:

A1=0π4(cos(x)sin(x))dx=21A_1 = \int_{0}^{\frac{\pi}{4}} (\cos(x) - \sin(x)) \, dx = \sqrt{2} - 1

For x[π4,π2]x \in [\frac{\pi}{4}, \frac{\pi}{2}]:

A2=π4π2(sin(x)cos(x))dx=1+2A_2 = \int_{\frac{\pi}{4}}^{\frac{\pi}{2}} (\sin(x) - \cos(x)) \, dx = -1 + \sqrt{2}

For x[π2,π]x \in [\frac{\pi}{2}, \pi]:

Here, sin(x)\sin(x) is always greater than cos(x)\cos(x). A3=π2π(sin(x)cos(x))dxA_3 = \int_{\frac{\pi}{2}}^{\pi} (\sin(x) - \cos(x)) \, dx Let's compute A3A_3: [ A_3 = \left[-\cos(x) - \sin(x)\right]_{\frac{\pi}{2}}^{\pi} = \left[-\cos(\pi) - \sin(\pi)\right] - \left[-\cos\left(\frac{\pi}{2}\right) - \sin\left(\frac{\pi}{2}\right)\right] ] [ = \left[1 - 0\right] - \left[0 - 1\right] = 1 + 1 = 2 ]

Step 4: Add the Three Areas Together

A=A1+A2+A3=(21)+(1+2)+2=222+2=22A = A_1 + A_2 + A_3 = (\sqrt{2} - 1) + (-1 + \sqrt{2}) + 2 = 2\sqrt{2} - 2 + 2 = 2\sqrt{2}

Thus, the area of the region enclosed by the curves y=sin(x)y = \sin(x) and y=cos(x)y = \cos(x) on the interval [0,π][0, \pi] is:

22\boxed{2\sqrt{2}}

This result shows that the area is larger when the interval is extended to [0,π][0, \pi] compared to [0,π2][0, \frac{\pi}{2}].

Do you have any questions, or would you like further details?


Here are 5 related questions to explore:

  1. How would the area change if the interval was [0,2π][0, 2\pi]?
  2. Can you find the area between y=sin(2x)y = \sin(2x) and y=cos(2x)y = \cos(2x) on [0,π][0, \pi]?
  3. What happens if we only consider the interval [π2,π][\frac{\pi}{2}, \pi]?
  4. How do the areas compare if we consider y=sin(x)y = \sin(x) and y=cos(x)y = -\cos(x) on [0,π][0, \pi]?
  5. What if the curves were y=sin(x)y = \sin(x) and y=sin(xπ4)y = \sin(x - \frac{\pi}{4}) on [0,π][0, \pi]?

Tip: Extending the interval often requires recalculating areas based on the changing positions of the curves relative to each other. Always check which curve is above the other within each subinterval.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Integration
Trigonometry

Formulas

Area between curves formula

Theorems

-

Suitable Grade Level

Advanced High School