Bytelearn - cat image with glassesAI tutor

Welcome to Bytelearn!

Let’s check out your problem:

Let 
f be the function defined by 
f(x)=sin((pi)/(4)x). What is the average value of 
f on the interval 
[(4)/(3),(8)/(3)] written in simplest form?

Let f f be the function defined by f(x)=sin(π4x) f(x)=\sin \left(\frac{\pi}{4} x\right) . What is the average value of f f on the interval [43,83] \left[\frac{4}{3}, \frac{8}{3}\right] written in simplest form?

Full solution

Q. Let f f be the function defined by f(x)=sin(π4x) f(x)=\sin \left(\frac{\pi}{4} x\right) . What is the average value of f f on the interval [43,83] \left[\frac{4}{3}, \frac{8}{3}\right] written in simplest form?
  1. Calculate difference: To find the average value of a continuous function f(x)f(x) on the interval [a,b][a, b], we use the formula:\newlineAverage value = 1(ba)abf(x)dx\frac{1}{(b-a)} \int_{a}^{b} f(x) \, dx\newlineHere, f(x)=sin(π4x)f(x) = \sin\left(\frac{\pi}{4}x\right), a=43a = \frac{4}{3}, and b=83b = \frac{8}{3}.
  2. Set up integral: First, we calculate the difference bab - a:ba=8343=43b - a = \frac{8}{3} - \frac{4}{3} = \frac{4}{3}
  3. Simplify coefficient: Now, we set up the integral to find the average value:\newlineAverage value = 1(43)\frac{1}{\left(\frac{4}{3}\right)} * 4383sin(π4x)dx\int_{\frac{4}{3}}^{\frac{8}{3}} \sin\left(\frac{\pi}{4}x\right) dx
  4. Use substitution method: We can simplify the coefficient in front of the integral: \newline(1/((4)/(3)))=(3)/(4)(1/((4)/(3))) = (3)/(4)\newlineSo, Average value = (3)/(4)×(4)/(3)(8)/(3)sin((π)/(4)x)dx(3)/(4) \times \int_{(4)/(3)}^{(8)/(3)} \sin((\pi)/(4)x) \, dx
  5. Change limits of integration: To integrate sin(π4x)\sin\left(\frac{\pi}{4}x\right), we use the substitution method. Let u=π4xu = \frac{\pi}{4}x, then du=π4dxdu = \frac{\pi}{4}dx, or dx=4πdudx = \frac{4}{\pi}du.
  6. Write integral in terms of uu: We also need to change the limits of integration. When x=43x = \frac{4}{3}, u=π443=π3u = \frac{\pi}{4}\cdot\frac{4}{3} = \frac{\pi}{3}. When x=83x = \frac{8}{3}, u=π483=2π3u = \frac{\pi}{4}\cdot\frac{8}{3} = \frac{2\pi}{3}.
  7. Simplify integral further: Now we can write the integral in terms of uu:
    Average value = 34×π32π3sin(u)×4πdu\frac{3}{4} \times \int_{\frac{\pi}{3}}^{\frac{2\pi}{3}} \sin(u) \times \frac{4}{\pi} \, du
  8. Integrate sin(u)\sin(u): We can simplify the integral further by taking out the constant 4π\frac{4}{\pi}:
    Average value = 34×4π×π32π3sin(u)du\frac{3}{4} \times \frac{4}{\pi} \times \int_{\frac{\pi}{3}}^{\frac{2\pi}{3}} \sin(u) \, du
  9. Evaluate antiderivative: Now we integrate sin(u)\sin(u) from π3\frac{\pi}{3} to 2π3\frac{2\pi}{3}:sin(u)du=cos(u)+C\int \sin(u) \, du = -\cos(u) + C So, we need to evaluate cos(u)-\cos(u) from π3\frac{\pi}{3} to 2π3\frac{2\pi}{3}.
  10. Evaluate bounds: Evaluating the antiderivative at the bounds gives us: cos(2π3)(cos(π3))-\cos\left(\frac{2\pi}{3}\right) - \left(-\cos\left(\frac{\pi}{3}\right)\right)
  11. Multiply by coefficient: We know that cos(π3)=12\cos\left(\frac{\pi}{3}\right) = \frac{1}{2} and cos(2π3)=12\cos\left(\frac{2\pi}{3}\right) = -\frac{1}{2}. So, (12)(12)=12+12=1-(-\frac{1}{2}) - (-\frac{1}{2}) = \frac{1}{2} + \frac{1}{2} = 1
  12. Final average value: Now we multiply this result by the coefficient we found earlier:\newlineAverage value = (34)×(4π)×1(\frac{3}{4}) \times (\frac{4}{\pi}) \times 1
  13. Final average value: Now we multiply this result by the coefficient we found earlier:\newlineAverage value = (34)×(4π)×1(\frac{3}{4}) \times (\frac{4}{\pi}) \times 1 Simplifying this expression gives us the final average value:\newlineAverage value = (3π)(\frac{3}{\pi})

More problems from Write variable expressions for arithmetic sequences