Density of a rod w/ density function p(x)= 5sin(pi/4)x

[confused_07]

Find the mass M (in grams) of a rod coinciding w/ the interval [0,4] which has the density function p(x)= 5sin(pi/4)x.

delta x= 4/n
delta Mi= [5sin(pi/4)xi]

M= lim n-> infinity int[0,4] [5sin(pi/4)x) dx
= [-(20/pi) sin (pi/4)x] [0,4]
= [-(20/pi) sin (pi/4) (4)]
= -.349

I know that's not right as I can not have negative grams. Can you see where I went wrong? Thanks....

 

[confused_07]

I see it....... I put sin instead of cosine......

Redid the math, still come out negative... -25.462 ?