Sunday, September 1, 2013

Given dy/dx=square root(-4x^2+8x+12), what is the function y?

The derivative of y is given as dy/dx =
sqrt(-4x^2+8x+12)


y' = sqrt [
-4x^2+8x+12]


=> 2*sqrt [-x^2 + 2x +
3]


=> 2*sqrt [ -(x^2 - 2x + 1) +
4]


=> 2*sqrt [ -(x - 1)^2 +
4]


y = Int[ y'  dx]


=>
2* Int [ sqrt [ 4 - (x - 1)^2] dx]


Let x - 1 = 2*sin
u


dx = 2*cos u du


2* Int [
sqrt [ 4 - (x - 1)^2] dx]


=>2*Int [ sqrt (4 - 4 (sin
u)^2) 2 cos u du]


=> 2*[Int[ 4*sqrt(1 - (sin u)^2)
cos u du]


=> 2*[Int[ 4*sqrt((cos u)^2) cos u
du]


=> 2*[Int[ 4*(cos u)^2
du]


=> 2*[Int[ 2*(1 + cos 2u)
du]


=> 2*[Int[ 2 + 2*cos 2u
du]


=> 2*2*u + 2*sin 2u +
C


=> 4u + 2*sin 2u +
C


=> 4*arc sin ((x - 1)/2) + 2*sin(2*arc sin ((x -
1)/2) + C


The function y = 4*arc sin ((x -
1)/2) + 2*sin(2*arc sin (x - 1)/2) + C

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