Sine Theorem for Angle A

I remember that year when the sun fell on the side of your face and someone was throwing paper airplanes outside the window, I took this photo as a self-righteous souvenir. [The first science of science and the mastery of one subject of liberal arts] 1v1, HE, double academic master in arts and sciences. Intention: I will give you my time to make you happy. I promise that in this life, the mountains and seas will never separate us, and we will never give up.