The sum of the diagonal elements of a matrix $A$ is called the trace of $A$ and is denoted by $tr(A)$. Which of the following statements about the trace are true?
- $\text{tr(A+B)=tr(A)+tr(B)}$
- $\text{tr(2A)=2tr(A)}$
- $\text{tr($A^T$)=tr(A)}$
- $\text{tr($A^{-1}$)=tr(A)}$