Solution 1:
they are $$(2k+1)\cdot \frac{\pi}{2}$$ with $$k \in \mathbb{Z}$$
Solution 2:
You can go with $2\mathbb Z +1$
Notation for every odd integer number
Solution 1:
they are $$(2k+1)\cdot \frac{\pi}{2}$$ with $$k \in \mathbb{Z}$$
Solution 2:
You can go with $2\mathbb Z +1$