Solution
= Solution
The <trace> is unchanged by <similarity>, so in the same <eigenbasis>
$$
\boxed{\operatorname{tr}H=\lambda_1+\lambda_2.}
$$
= Solution
The <trace> is unchanged by <similarity>, so in the same <eigenbasis>
$$
\boxed{\operatorname{tr}H=\lambda_1+\lambda_2.}
$$