Inner product on direct sum of Hilbert spaces

Question

Let $H_1$ and $H_2$ are two different Hilbert spaces then how can we define the inner product on $H_1\oplus H_2$

Answer 1

Like this:

$$\langle (x,y),(z,w)\rangle_{H_1\oplus H_2}=\langle x,z\rangle_{H_1}+\langle y,w\rangle_{H_2}$$