I need help with these math prob plz?

Question

1). let the region be bounded by x^2 + y^2=9 be the base of a solid. What is the volume if the cross sections taken perpendicular to the base are isosceles right triangles

2). A cylindrical tank 12 ft high with radius of 8 ft is buried so that the top of the tank is 3 ft below ground level. Write down the integral that gives the amount of work done in pumping a full tank of oil up to ground level. Use 50 pounds per cubic foot as the weight-density of oil.

3). What is the arc length of one arc of the sine curve y=sin x,....when x is between 0 and pie

Answer 1

1. the solid is a cone. you can't find out the area if you are not given at least one more information eg: at which point is the tip of the cone.

3. to find the arc length , let x=t, and y= sint.

mini arc length is sqrt((dx)^2+(dsint)^2)

so integrate that with respect to t from 0 and pi