Rotation about a point

Question

Daniel Campbell 2018-11-15

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https://ww2.mathworks.cn/matlabcentral/answers/430093-rotation-about-a-point

编辑： Jim Riggs 2018-11-15

Hi there I have been given a problem:

"A triangle is defined by the points (1, 1), (2, 4) and (7, 2). Using the three constituent simple transformations, transform the triangle with a rotation about the point (1, 3) by 60◦ anti-clockwise".

If I am being honest I have no idea how to start this

Any help would be great

Daniel

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madhan ravi 2018-11-15

why do you close the question?

madhan ravi 2018-11-15

If you keep closing the question , you wont get any further help hereafter

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Answer 1

Jim Riggs 2018-11-15

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https://ww2.mathworks.cn/matlabcentral/answers/430093-rotation-about-a-point#answer_347168

编辑：Jim Riggs 2018-11-15

If you want the equations they are as follows;

X = [1 2 7 1];
Y = [1 4 2 1];
ang = -60  % degrees
Xc = 1;  % X cener of rotation
Yc = 3;  % Y center of rotation
% Shift X/Y to the rotation center
Xshift = X - Xc;        
Yshift = Y - Yc;
% Rotate the coordinates
Xsrot =  Xshift*cosd(ang) + Yshift*sind(ang);
Ysrot = -Xshift*sind(ang) + Yshift*cosd(ang);
% Shift the rotated coordinates back to the original reference center
Xrot = Xsrot + Xc;
Yrot = Ysrot + Yc;

Now X,Y is the original triangle and Xrot,Yrot is the rotated triangle

This can be shortened to:

X = [1 2 7 1];
Y = [1 4 2 1];
ang = -60;  % degrees
Xc = 1;
Yc = 3;
Xrot =  (X-Xc)*cosd(ang) + (Y-Yc)*sind(ang) + Xc;
Yrot = -(X-Xc)*sind(ang) + (Y-Yc)*cosd(ang) + Yc;

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Answer 2

madhan ravi 2018-11-15

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https://ww2.mathworks.cn/matlabcentral/answers/430093-rotation-about-a-point#answer_347148

编辑：madhan ravi 2018-11-15

在 MATLAB Online 中打开

x=[1 2 7 1];
y=[1 4 2 1];
fig=figure
h=plot(x,y)
center = [1 3];
rotate(h,center,-60)
title('ROTATED TRIANGLE @CENTER (1,3) anticlockwise')
print(fig,'Rotated_triangle','-dpng')
fig1=figure
plot(x,y)
title('ORIGINAL TRIANGLE')
print(fig1,'Orignal_triangle','-dpng')