New to MATLAB, Need basic help

[SaRCaZZM]

Homework Statement

I need help solving for d, in the really long equation below. However, whenever I insert the following command (see below), I get 'is not a valid equation or expression', but I can't figure out why.

Homework Equations

((cot(104.789d))^2) + (((cot(104.789d))^2)*(1 + (-1.339*(10^-3)))*((sin(209.58d))^2))=-0.3939

The Attempt at a Solution

solve('((cot(104.789d))^2) + (((cot(104.789d))^2)*(1 + (-1.339*(10^-3)))*((sin(209.58d))^2))=-0.3939','d')

 

[CEL]

Homework Statement

I need help solving for d, in the really long equation below. However, whenever I insert the following command (see below), I get 'is not a valid equation or expression', but I can't figure out why.

Homework Equations

((cot(104.789d))^2) + (((cot(104.789d))^2)*(1 + (-1.339*(10^-3)))*((sin(209.58d))^2))=-0.3939

The Attempt at a Solution

solve('((cot(104.789d))^2) + (((cot(104.789d))^2)*(1 + (-1.339*(10^-3)))*((sin(209.58d))^2))=-0.3939','d')

I suppose that when you write cot(104.789d) you really mean cot(104.789*d). The same with the arguments of the other trigonometric functions.

 

[Ouabache]

I would recheck some examples of MATLAB's "solve" function. Your use of single quotes around the variable at the end of your expression, looks odd to me.

 

[gboye27a]

1
Ask the user for inputs of the variables start, stop, inc and a. At runtime please enter values of 0, 30, 0.1 and 2, respectively. Plot the equation alt = sin(pi/4) + a•(t-5)2, where a is 2 and t varies from 0 to 30 with a step size of 0.1 in a figure 2. Use an appropriate FOR loop to generate and store the values of t and alt. Add a title, xlabel and ylabel to the plot. Remember to clear at the beginning and pause at the end of the code.


2
For the same “alt” equation above, use a WHILE loop to solve for the time t (starting from 0) at which alt crosses 600 but this time use inc of 0.01 instead of 0.1. Use the command sprintf to create an output message displaying the time at which this occurs (label your answer clearly). Remember to clear at the beginning and pause at the end of the code.

 

[alphy]

I understand the frustration of trying to learn a new programming language like MATLAB. It can be overwhelming and confusing at first, but with practice and patience, you will become more comfortable with it.

In this particular case, the error you are receiving is likely due to the use of trigonometric functions in your equation. MATLAB requires the use of radians, not degrees, for trigonometric functions. So, when inputting the angle values, make sure to convert them to radians first. For example, 104.789 degrees would be 1.826 radians.

Additionally, it is good practice to break down complex equations into smaller, more manageable parts when using MATLAB. This can help identify any errors or issues more easily. So, you could try solving for each individual term (e.g. (cot(104.789d))^2) and then combining them in the final equation.

I hope this helps and good luck with your homework! Remember to always check your units and double check your equations for any potential errors. Science is all about attention to detail.