Rotation about a point

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

[madhan ravi]

why do you close the question?

[madhan ravi]

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

Answer 1

[Jim Riggs]

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;

Answer 2

[madhan ravi]

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')

[Daniel Campbell]

Hi there this is great but how do you print the rotated triangle as well?

[madhan ravi]

if my answer worked make sure to accept the answer

[Daniel Campbell]

I need to display the triangle and the rotated triangle.

[madhan ravi]

see edited answer