MATLAB question on Chapter 4

How I find the minimum length of the cord?

I figured out how to get the equation however, when I write in MATLAB I cannot seem to get a response since x is an array

This is what I have so far:

%% Problem 10

%Create x

% Let H1 = x

x = [50:0.1:200];

H1 = x;

% Creating an array that ranges from 50 to 200 with increments of 0.1

% We do this because the image shows us that the length of the cable for

% house1 (H1) cannot be more than 210 ft

% We know want to find the lenght of house2 and 3 (H2 & H3).

% The image shows us that we can form a triangle at the corner of H2 and

% H3.

% The length between the two is 210 -x and the height of each starting at

% the 210-x length is 80ft

% So we will use the pythagorean theorem to find the missing side for H2

% and H3

% Note that both H2 and H3 have the same dimensions so we will use one

% equation and double it.

% H2= H3= y = sqrt(80^2 + (210-H1)^2)

y = sqrt(80^2 + (210-H1)^2);

% To find the total length

total = H1 + 2* sqrt(80^2 + (210-H1)^2)

[Miriam Marroquin]

Here is the question:

The electricity supply cables of the three houses shown are connected to a pole as shown. Write a MATLAB program that determines the location of the pole (distance x) that minimizes the total length of the cables needed. In the program define a vector x with values ranging from 50 to 200 with increments of 0.1. Use this vector to calculate the corresponding values of total length of the cables. Then use MATLAB’s built-in function min to find the value of x that corresponds to the shortest length of cables.

Answer 1

[Madhav Thakker]

Hi Miriam,

The variable H1 is a matrix of size [1, 1501] and the command

y = sqrt(80^2 + (210-H1)^2); 

tries to multiply a matrix of size [1. 1501] with itself, which throws an error. What you instead need to do is take the square of each element for which you can use dot operator. Example -

y = sqrt(80^2 + (210-H1).^2);
total = H1 + 2* sqrt(80^2 + (210-H1).^2)
min(total)

Hope this helps.

[Miriam Marroquin]

Thanks for the guidance, I forgot about the element-by-element operation!