Really need help, need to check my answers. These are parts of a review so..

#1 Region M is bounded by the x-axis, x=4 and the graph of $\displaystyle LN(x)$

is the interval 1 to 4?

a)find the volume of the solid created by revolving M around y=-4

I got 70.958 as the area

b)find the volume of the solid created by revolving M around y=7

113.964

c)let region M be the base of a solid whose cross sections perpendicular to the x-axis are isosceles right triangles, find the volume of the solid.

This is the one I don't understand. Please help me setup this problem.

d)let region M be the base of a solid whose cross sections perpendicular to the x-axis are circles, find the volume of the solid.

not sure how to do this one either.

#2Region Q is bounded by the y-axis, the line y=5 and the curve e(x)

Let region R be the base of a solid whose cross sections perpendicular to the x-axis are semi-circles, find the volume of the solid.

Is the interval for the integral 0 to 1.609? And then what do I do? Need help setting it up.

#3 Region T is bounded by the x-axis and the graphs of $\displaystyle \sqrt{x}$ and $\displaystyle -0.2x^2+6$

This one is really confusing me. All I know is the interval 0 to 4.415. I don't understand how you'd solve it on the y-axis. The x-axis was easier to understand.

a) find the volume of the solid created by revolving T around the y-axis

b) around x=-3

c) around x=10

d) let T be the base of a solid whose cross sections perpendicular to the y-axis are squares, find the volume of the solid.