Syntax error when dividing by a matrix variable

I keep getting an error with this line of code:

q=(R*sin(theta))./(1-cos(theta)*cos(t).);

R and theta are constants. t is given by the following

N = 100

dt = 2*pi/N;

t=(0:dt:2*pi)';

Since t contains a matrix of values, I thought the correct way to include this was through cos(t)., but Matlab keeps throwing up the following error:

"Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters."

If I just use cos(t) [without the period], then there is no error but all of the values of q in the resulting matrix are identical. I don't understand what I am doing wrong.

[Stephen23]

"Syntax error when dividing by a matrix variable"

That error is unrelated to any division operator.

"Since t contains a matrix of values, I thought the correct way to include this was through cos(t)., but Matlab keeps throwing up the following error"

The documentation for https://www.mathworks.com/help/matlab/ref/double.cos.html does not mention dots anywhere. It states that it accepts one "Input angle in radians, specified as a scalar, vector, matrix, multidimensional array, table, or timetable". So cos() already accepts a vector.

"If I just use cos(t) [without the period], then there is no error but all of the values of q in the resulting matrix are identical."

Lets try it:

theta = 1;
R = 1;
N = 100;
dt = 2*pi/N;
t = (0:dt:2*pi)'; 
q = (R*sin(theta))./(1-cos(theta)*cos(t))

q = 101×1

1.8305 1.8263 1.8137 1.7932 1.7653 1.7309 1.6909 1.6463 1.5981 1.5474 1.4949 1.4416 1.3883 1.3354 1.2835

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They look different to me.

[Walter Roberson]

@Robert Demyanovich

You have mistaken the purpose of the dot in expressions such as A./B . It is not (A.) / B with . being some operator. Instead, it is an operator named ./ just the same way as ~= and <= are the names of single operators.

Answer 1

[Star Strider]

The additional period (or decimal point) may be confusing the interpreter.

q=(R*sin(theta))./(1-cos(theta)*cos(t).);

^

That error is only thrown with the dot present, not otherwise.

q=(R*sin(theta))./(1-cos(theta)*cos(t));

q=(R*sin(theta))./(1-cos(theta)*cos(t).);

Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters.

.