The sine cosine formulas are interchangeable:
sin（π/2－α）＝cosα。
cos（π/2－α）＝sinα。
sin（π/2＋α）＝cosα。
cos（π/2＋α）＝－sinα。
cos（π－α）＝－cosα。
sin（3π/2－α）＝－cosα。
cos（3π/2－α）＝－sinα。
sin（3π/2＋α）＝－cosα。
cos（3π/2＋α）＝sinα。
Exchange pithy formula: odd, variable and even are unchanged, and the symbol looks at the quadrant.
Sine, a mathematical term, in a right triangle, the ratio of the opposite side of any acute angle ∠ A to the hypotenuse is called the sine of ∠ A, which is recorded as sinA (abbreviated from the English word sine), that is, sinA=the opposite side/hypotenuse of ∠ A.
Cosine (cosine function), a kind of trigonometric function. In Rt △ ABC (right triangle), ∠ C=90 ° (as shown in the overview diagram), the cosine of ∠ A is the hypotenuse of its adjacent side than the triangle, that is, cosA=b/c, or cosa=AC/AB. Cosine function: f (x)=cosx (x ∈ R).
