MATLAB: Am I get discontinuous plot

plot 2d

Why am I get discontinuous plot?

    x = -2*pi:.1:2*pi;
y = 2e-6*sin(x).*cos(x)/(10.5e-12*sin(x).^2+13.8e-12*cos(x).^2);

Use ./ instead of /

x = -2*pi:.1:2*pi;
y = 2e-6*sin(x).*cos(x)./(10.5e-12*sin(x).^2+13.8e-12*cos(x).^2);
plot(x,y)

Draw it continuous segment by continuous segment, OR put a NaN between the continuous parts. Or just let it connect the discontinuous parts.

Have you considered a stairs plot?

x = -2:0.01:2;
y = cos(x)+exp(-1/2*x.^2).*sin(6*x);
plot(x,y)