graph not plotting anything

When i plot the following graph nothing appears.

theta = linspace(0,2*pi, 1000);
d2b = -(a*cos(theta)*c^2 - a^2*sin(theta).^2.^(3/2) + a^3*sin(theta).^4 + a*c^2*cos(theta).^2 - a*c^2*sin(theta).^2)/(c^2 - a^2*sin(theta).^2).^(3/2);
plot(theta,d2b, 'g');
xlim([0,2*pi])
 
figure(3)
plot(theta,d2b,'g')
set(gca,'XTick',0:pi/2:2*pi) 
set(gca,'XTickLabel',{'0','pi/2','pi','3*pi/2','2*pi'})

Answer 1

[KSSV]

You need to use element by element by division i.e. ./ in the formula.

theta = linspace(0,2*pi, 1000);
d2b = -(a*cos(theta)*c^2 - a^2*sin(theta).^2.^(3/2) + a^3*sin(theta).^4 + a*c^2*cos(theta).^2 - a*c^2*sin(theta).^2)./(c^2 - a^2*sin(theta).^2).^(3/2);
plot(theta,d2b, 'g');
xlim([0,2*pi])
 
figure(3)
plot(theta,d2b,'g')
set(gca,'XTick',0:pi/2:2*pi) 
set(gca,'XTickLabel',{'0','pi/2','pi','3*pi/2','2*pi'})