Plot the part of the cylinder x^2 + z^2 = 1 for y ≥ 0 , 0 ≤ z ≤ − y^2 + 1 . Can someone help me

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dang thai bao 2021-5-11

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https://ww2.mathworks.cn/matlabcentral/answers/827230-plot-the-part-of-the-cylinder-x-2-z-2-1-for-y-0-0-z-y-2-1-can-someone

回答： DGM 2021-5-11

i don't know how to do it

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Jan 2021-5-11

What have you tried so far?

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Answer 1

DGM 2021-5-11

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https://ww2.mathworks.cn/matlabcentral/answers/827230-plot-the-part-of-the-cylinder-x-2-z-2-1-for-y-0-0-z-y-2-1-can-someone#answer_697295

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This is a rather simple approach:

n = 200;
th = linspace(0,pi,n);
x = linspace(-1,1,n);
y = linspace(0,1,n).';
zc = repmat(sin(th),[n 1]);
xc = cos(th);
zp = repmat(-y.^2+1,[1 n]);
zc(zc>zp) = NaN;
surf(xc,y,zc); hold on
shading flat
axis equal

If you want to be assured that the trimmed face follows a parabola:

n = 200;
th = linspace(0,pi,n);
x = linspace(-1,1,n);
y = linspace(0,1,n).';
zc = repmat(sin(th),[n 1]);
xc = cos(th);
zp = repmat(-y.^2+1,[1 n]);
zc(zc>zp) = NaN;
surf(xc,y,zc); hold on
surf(x,y,zp,'facealpha',0.4);
shading flat
axis equal