Math Problem Statement

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Find the absolute minimum and absolute maximum values of the function y = (1/sqrt(2))sin^2(x) + sin(x) on the interval [π/3, 3π/2].

Solution

The given function is:

y=12sin2(x)+sin(x)y = \frac{1}{\sqrt{2}} \sin^2(x) + \sin(x)

You are asked to find the absolute minimum and maximum values of yy on the interval:

[π3,3π2]\left[ \frac{\pi}{3}, \frac{3\pi}{2} \right]

Steps to Solve:

  1. Take the derivative of yy: y=12sin2(x)+sin(x)y = \frac{1}{\sqrt{2}} \sin^2(x) + \sin(x) Using the chain rule, the derivative of yy with respect to xx is: dydx=ddx(12sin2(x))+ddx(sin(x))\frac{dy}{dx} = \frac{d}{dx} \left( \frac{1}{\sqrt{2}} \sin^2(x) \right) + \frac{d}{dx} (\sin(x)) Apply the chain rule to the first term: dydx=22sin(x)cos(x)+cos(x)\frac{dy}{dx} = \frac{2}{\sqrt{2}} \sin(x) \cos(x) + \cos(x) Simplify: dydx=2sin(x)cos(x)+cos(x)\frac{dy}{dx} = \sqrt{2} \sin(x) \cos(x) + \cos(x) Using the double-angle identity sin(2x)=2sin(x)cos(x)\sin(2x) = 2 \sin(x) \cos(x), we get: dydx=22sin(2x)+cos(x)\frac{dy}{dx} = \frac{\sqrt{2}}{2} \sin(2x) + \cos(x)

  2. Find critical points: Set the derivative equal to 0: 22sin(2x)+cos(x)=0\frac{\sqrt{2}}{2} \sin(2x) + \cos(x) = 0 Solve this equation for xx.

  3. Check boundary points and critical points: Evaluate the function yy at the boundaries x=π3x = \frac{\pi}{3} and x=3π2x = \frac{3\pi}{2}, as well as at any critical points found in step 2. The largest value will be the absolute maximum, and the smallest value will be the absolute minimum.

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Math Problem Analysis

Mathematical Concepts

Calculus
Derivatives
Critical Points
Maxima and Minima
Trigonometric Functions

Formulas

y = (1/√2)sin²(x) + sin(x)
Derivative of sin²(x) = 2sin(x)cos(x)
Derivative of sin(x) = cos(x)
Critical points: set dy/dx = 0

Theorems

Fundamental Theorem of Calculus
Trigonometric Double Angle Identity (sin(2x) = 2sin(x)cos(x))

Suitable Grade Level

Grade 12 - College Calculus