$20^\circ <\varphi<25^\circ$20^\circ <\varphi<25^\circ

$25^\circ <\varphi<30^\circ$25^\circ <\varphi<30^\circ

$30^\circ <\varphi<35^\circ$30^\circ <\varphi<35^\circ

$35^\circ <\varphi<40^\circ$35^\circ <\varphi<40^\circ