draw a function composed of sin and cos

i encounter an error when trying ti plot this function

x=-pi:0.1*pi:pi;
y1=100*sqrt(2*pi)/sqrt(0.05*pi).*cos(x/2)*(1.-cos(x/2.)*sin(x/2.)*sin(3.*x/2.));
figure
plot(x,y1)

Answer 1

[Star Strider]

Use element-wise operations

y1=100*sqrt(2*pi)/sqrt(0.05*pi).*cos(x/2).*(1.-cos(x/2.).*sin(x/2.).*sin(3.*x/2.));

↑ ↑ ↑ ↑

See Array vs Matrix Operations for details.

x=-pi:0.1*pi:pi;
y1=100*sqrt(2*pi)/sqrt(0.05*pi).*cos(x/2).*(1.-cos(x/2.).*sin(x/2.).*sin(3.*x/2.));
figure
plot(x,y1)

.

[Steven Lord]

What @Star Strider has written is correct but one section might be slightly misleading for newer users.

% (1.-cos(x/2.).*sin(x/2.).*sin(3.*x/2.))

That first part may make you think there is an operator .- that does element-wise subtraction. But that's not the case. That period is not part of the operator but part of the number itself, since subtraction already applies element-wise. [There's also no .+ operator; just + is sufficient.]

x = 1.; % one
y = 1; % also one
x == y % true

ans = logical
   1

Note that something like this would error instead.

x = 1.1 .- 1

Invalid use of operator.

Error in connector.internal.fevalMatlab

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