How do you find the arc length of the curve y=(5sqrt7)/3x^(3/2)-9y=573x329 over the interval [0,5]?

1 Answer
Jun 16, 2018

s=int_0^5sqrt(1+175/4x)color(white).dx=1/525(879^(3/2)-8)s=501+1754x.dx=1525(879328)

Explanation:

The arc length of a function yy on the interval [a,b][a,b] is given by:

s=int_a^bsqrt(1+(dy/dx)^2)color(white).dxs=ba1+(dydx)2.dx

Here:

y=(5sqrt7)/3x^(3/2)-9y=573x329

dy/dx=(5sqrt7)/3(3/2x^(1/2))=(5sqrt7)/2x^(1/2)dydx=573(32x12)=572x12

Then the arc length desired is:

s=int_0^5sqrt(1+((5sqrt7)/2x^(1/2))^2)color(white).dxs=50 1+(572x12)2.dx

s=int_0^5sqrt(1+175/4x)color(white).dxs=501+1754x.dx

Let u=1+175/4xu=1+1754x, which implies that du=175/4dxdu=1754dx. Moreover, note the change of bounds of the integral under this substitution: x=0=>u=1x=0u=1 and x=5=>u=879/4x=5u=8794. The integral is then:

s=4/175int_1^(879//4)u^(1/2)color(white).dus=4175879/41u12.du

Integrating using the power rule for integration:

s=4/175(2/3u^(3/2))|_1^(879//4)s=4175(23u32)879/41

s=8/525((879/4)^(3/2)-1^(3/2))s=8525((8794)32132)

s=8/525(879^(3/2)/8-1)s=8525(8793281)

s=1/525(879^(3/2)-8)s=1525(879328)