# Math Help - Definite Intergral Post

1. ## Definite Intergral Post

I'm a little stumped the equation is x sqrt (1-x^4) using substitution. Thanks sososososo much in advance.

2. x^2=sin(y) is a good substitution
dx=1/2 cos(y)/sin^.5(y) dy
sqrt(1-x^4)=cos(y)

you will be integrating 1/2 cos^2(y) dy

3. Originally Posted by samer_guirguis_2000
x^2=sin(y) is a good substitution
dx=1/2 cos(y)/sin^.5(y) dy Mr F remarks: ${\color{red}dx = \frac{1}{2} \frac{\cos y}{x}}$ is sufficient - there's no need to express x in terms of y.

sqrt(1-x^4)=cos(y)

you will be integrating 1/2 cos^2(y) dy
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