以原点为中心，逆时针旋转角度
θ
\theta
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−
y
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y
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s
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x'=rcos(\theta+\phi)=rcos\theta cos\phi-rsin\theta sin\phi=xcos\theta-ysin\theta \\ y'=rsin(\theta+\phi)=rsin\theta cos\phi+rcos\theta sin\phi=xsin\theta+ycos\theta
x′=rcos(θ+ϕ)=rcosθcosϕ−rsinθsinϕ=xcosθ−ysinθy′=rsin(θ+ϕ)=rsinθcosϕ+rcosθsinϕ=xsinθ+ycosθ
d
e
t
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A
)
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1
det(A)=1
det(A)=1旋转后图形面积不变
A
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[
c
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]
A=\begin{bmatrix} cos\theta & -sin\theta\\ sin\theta & cos\theta \end{bmatrix}
A=[cosθsinθ−sinθcosθ]
x1 = [0;0];
x2 = [1;0];
x3 = [1;1];
x4 = [0;1];
x = [x1,x2,x3,x4,x1];
A = [0.866 -0.5;0.5 0.866];
y = A * x;
plot(x(1,:),x(2,:), 'b')
hold on
plot(y(1,:),y(2,:),'r')
axis([-1 1.5 0 1.5])
grid on
Processed:
0.017, SQL:
10
