- #1

indigo1

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## Homework Statement

if d(x)=x+2cosx represents the distance traveled by a particle from x=0 to x= 2pi.Find an x value in (0,2pi) for which the instantaneous velocity equals the average velocity.

## The Attempt at a Solution

This question is a direct application of the mean value theorem (LMVT)

D(x) = x + 2cos(x)

∴ D(0) = 0 + 2cos(0) = 2

∴ D(2pi) = 2π + 2cos(2π) = 2(π + 1)

∴ Average velocity = Total distance/Total time

= [D(2π) - D(0)]/(2π - 0)

= (2 + 2π - 2)/(2π)

= 1 m/s

Instantaneous velocity =D ' (x)

∴ v(t) = D'(x) = 1 - 2sin(x)

Given that, to find 'c' such that D ' (c) = avg velocity = 1

∴ 1 - 2sin(c) = 1

∴ sin(c) = 0

∴ c = 0 or π

But 'c' needs to lie in (0,2π)

∴ At c = π, the average velocity = instantanoeus velocity = 1

ive been at this and I am just wondering if it's right?