Question: How can I validate if an object is of a certian class? I currently use 

```
get_class($obj) == 'User';

```

But it may look like `\KM\User` when I am elsewhere? I think this way maybe abit prone to developer error. Is there something like:

```
compare_class($obj1, User);
// or maybe
classof($obj) == User;

```

Answer: 
You can simply compute verything before:

plot 25-20+((2Pi0.3²)/(Pi10²)Sqrt[2\*980(1+(Pi10²)/(Pi10²))]t)² from 0 to 38

or

plot 25-20+((2\*0.3²)/(10²)Sqrt[2\*980(1+1)]t)² from 0 to 38

or 

25 - 20 + 4 \* 0.0000081 \* 3920\*t^2 from 0 to 38 (I have some factor wrong, but you get the idea)

just apply basic math to the constants and remove the middle (imaginary part) after applying the 2nd binomic formula.

There is nothing to do with complex numbers.
You are confused about the math. Square root of -25 is square root of 25\*(-1) and that is square root of 25 \* square root of -1 and that is 5i. Real part of that number is 0.

If you want the 5, just check for the sign of the number to be "rooted" and change it if it is negative.