I am havng trouble with plotting this curve.

Cables are used to suspend bridge decks and other structures. If a heavy uniform cable hangs suspended from its two endpoints, it takes the shape of a catenary curve whose equation is where a is the height of the lowest point on the chain above some horizontal reference line, x is the horizontal coordinate measured to the right from the lowest point, and y is the vertical coordinate measured up from the reference line. Let a % 10 m. Plot the catenary curve for !20 # x # 30 m. How high is each endpoint?

So far I have

a=10  , y=a*cosh(x/a), x=-20:0.01:30; and plot(x,y),xlabel('x'),ylabel('y')

Answer 1

[Matt J]

Since y depends on x, you must define x first:

 a=10 , 
 x=-20:0.01:30;
 y=a*cosh(x/a), 
 plot(x,y),xlabel('x'),ylabel('y')

[VIGNESH BALAJI]

@Matt J If I plot this script, why are the end points at different height, Can I know why this happens ?

[DGM]

The curve is symmetric about x=0; since the vector x is not symmetric about 0, the endpoints are not the same height.

a = 10; % the height of the curve at x=0
x = -30:0.01:30; % x is now symmetric
y = a*cosh(x/a);
plot(x,y),xlabel('x'),ylabel('y')

[VIGNESH BALAJI]

@DGM thank you for the nice explanation.

What should I do, if I want to draw a catenary at different heights entirely on positive x axis (with fixed y at both ends)?

I have been trying to do it.