Cartesian form of the equation of catenary is A. y = c cosh $$\frac{{\text{x}}}{{\text{c}}}$$ B. y = c sinh $$\frac{{\text{x}}}{{\text{c}}}$$ C. y = c tan $$\frac{{\text{x}}}{{\text{c}}}$$ D. y = c sin $$\frac{{\text{x}}}{{\text{c}}}$$

The correct answer is A.

The equation of a catenary is $y = c cosh \frac{x}{c}$, where $c$ is the length of the chain and $x$ is the horizontal distance from the lowest point of the chain.

The other options are incorrect because they do not represent the equation of a catenary.

Option B is the equation of a hyperbolic sine function.

Option C is the equation of a tangent function.

Option D is the equation of a sine function.