## anonymous 5 years ago i need someone to explaim how to figure surface areas of a cone

1. anonymous

2. anonymous

Is it closed on the bottom of the cone? If so, the surface area is:$SA = \pi*r*s+\pi*r^2$ where "s" is the length from the tip of the cone to the outer edge of the base. If it's an open cone, you can get rid of the pi*r^2 term.

3. amistre64

circumference of the base integrated thru the height, if that makes sense :)

4. amistre64

height for any given piece is (2-y) circumference for any given piece is (2pi(x)) x = -(7/2) y So; 2pi(-7/1)y dy from 0 to 2.... might need a second pair of eyes on that tho :)

5. amistre64

.... -7pi (S) (y)(2-y) dy | 0,2 -7pi (S) 2y - y^2 dy | 0,2 -7pi; y^2 - (y^3)/3 | 0,2 .... only (2) matters -7pi; 2^2 - (2^3)/3 -7pi (4 - (8/3)) = (12/3 - 8/3) -7pi (4/3) = -28pi/3 ; we can toss the (-) because it just means we used the wrong "side" and we are left with.. 28pi/3 ..... of which I have no idea if ii did it correctly :)