Question: "Is this triangle right-angled?" - where can I find functions and their uses/learn about the program outside of class

So the question I have to answer is:

"Given three positive numbers a, b, c, where c is the largest number, return true if the triangle with sides a, b and c is right-angled. Otherwise, return false."

This is my solution which doesn't work.

 function flag = isRightAngled(a, b, c)
  flag = true

function flag ~= isRightAngled(a, b, c) flag = false;

 end

The first part of the code works fine, and flag returns true when I run the code through test suite on cody courseworks, bolded code is what I added and doesn't work - which I need help with!

Thanks

[Roger Stafford]

Consult the pythagorean theorem

[Stephen23]

And the line

 function flag ~= isRightAngled(a, b, c) flag = false;

is not MATLAB syntax at all. Read the code help (red/orange underlines): they will help you to figure out why this is not valid syntax. Some of the problems in that line are:

• trying to define a nested function without a matching end.
• trying to define a function and allocate its output using ~=.
• Recursive function calling without any limits.

I suspect that none of these were intentional. To fix this you need to how to call functions, and how this is different to defining functions:

https://www.mathworks.com/help/matlab/getting-started-with-matlab.html

Answer 1

[Lewis Pole]

I have no idea how to implement a^2+b^2=c^2 into code

I was hoping someone could fix the whole code up and I could break it down to understand how to set code out, what does what, etc.

[Walter Roberson]

if a^2 + b^2 == c^2

... except you need to allow for round-off error.

http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F

Answer 2

[Jan]

d = a^2 + b^2 - c^2;

Now you cannot expect this to be exactly zeros due to the limited precision of floating point values in the double format. But you can check, if the result is "really small". See the command eps(x). The argument of eps() is important for the magnitude of the limit.

Answer 3

[Lewis Pole]

I'm still having problems..

function flag = isRightAngled(a, b, c) flag = true

end

Passes the flag=true test.

I don't know how to implement the function a^2+b^2=c^2 into code, which if it fails, should return flag=false to pass the flag=false test.

I know it might be asking to be spoon fed, but I haven't been taught anything yet and I'm just wanting to know more about code before I enter class next week. I believe breaking everything down is a more efficient way to learn.

[Stephen23]

"I'm just wanting to know more about code"

That is a great idea! The best place to start is by working through the introductory tutorials:

https://www.mathworks.com/help/matlab/getting-started-with-matlab.html

There are also video tutorials:

https://www.mathworks.com/videos/getting-started-with-matlab-68985.html

You will also find hundreds of online tutorials for getting started with MATLAB.

Answer 4

[Star Strider]

I would add a sort call, since the three sides could be input in any order:

a = rand;                                               % Input Argument
b = rand;                                               % Input Argument
c = rand;                                               % Input Argument

sides = sort([a b c]);                                  % Sort To Determine Order
test = sides(3)^2 - sides(2)^2 + sides(1)^2;            % Check Pythagorean Theorem
flag = abs(test < 1E-4);                                % Allow For Small Errors

[Walter Roberson]

test = sides(3)^2 - sides(2)^2 - sides(1)^2;            % Check Pythagorean Theorem

maybe ?

Answer 5

[Pen-Li (Ben) Yu]

flag = (0 == -a^2-b^2-c^2+2*max([a,b,c])^2)