00:01
So in this one, you want to find the surface of, area of the surface of revolution for x equals the natural log of 2y plus 1, and we're just setting it up where y is between 0 and 1.
00:19
So if we do it about the x -axis with respect to y, that's 0 to 1, 2 pi times y, excuse me, times the square root.
00:39
Of 1 plus dx, y squared, d .y.
00:51
Well, we know x, but x prime is 1 over 2y plus 1.
01:02
2 over 2 times 2 over 2 .2 .2.
01:09
It's really 2 .5 times the natural log 2 y plus 1.
01:17
Times the square root of 1 plus 2 squared 4, 2 y plus 2.
01:24
D .y.
01:26
If we solve that for y, we end up with y equal to the equal to the e to the 0...