你（不小心）尝试使用进行矩阵乘法*。

相反，你需要使用.*（Scilab docs，MATLAB docs）进行逐元素乘法。

同样，你应该使用元素方幂.^来平方第一个方程中的余弦项。

请参阅下面的修改后的代码中的注释...

r = 1;
l = 1;
% Note that t is an array, so we might encounter matrix operations!
t = linspace(0,2,10); 
% Using * on the next line is fine, only ever multiplying scalars with the array.
% Could equivalently use element-wise multiplication (.*) everywhere to be explicit.
% However, we need the element-wise power (.^) here for the same reason!
x = 2 * r * (cos(t)).^2 + l * cos(t);      
% We MUST use element-wise multiplication for cos(t).*sin(t), because the dimensions
% don't work for matrix multiplication (and it's not what we want anyway).
% Note we can leave the scalar/array product l*sin(t) alone, 
% or again be explicit with l.*sin(t) 
y = 2 * r * cos(t) .* sin(t) + l * sin(t);
plot (x,y);