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.
Taking the Square root of a general complex number can be done with the basic arithmetic operations on real numbers (plus taking square root of reals): <http://www.mathpropress.com/stan/bibliography/complexSquareRoot.pdf> (one technique is to utilise De Moivre's theorem: Any complex number a + bi can be written as `r(cos θ + i sin θ)` where

```
r = sqrt(a^2 + b^2),  cos θ = a/r, sin θ = b/r

```

**Update**: the formula `r(cos θ + i sin θ)` is originaly due to Euler, whereas De Moivre's theorem is

```
(a + ib)ⁿ = rⁿ(cos nθ + i sin nθ)

```