1、cos(a+b)= cosa cosb-Sina sinb cos(a-b)= cosa cosb+Sina sinb；

2、cos2a = cos2a-sin2a = 2 cos2a- 1 = 1-2 sin2a；

3、2 Sina cosb = sin(a+b)+sin(a-b)2 cosa sinb = sin(a+b)-sin(a-b)；

4. The general formula of geometric series is: an = a1* q (n-1);

5. The standard equation of a circle (x-a)2+(y-b)2=r2(a, B) is the center coordinate;

y=logax y=logae/x .

Reciting formulas and theorems in high school mathematics;

Trigonometric functions are functions, and quadrant symbols are labeled. Function image unit circle, periodic parity increase and decrease. The same angle relation is very important, and both simplification and proof are needed. At the vertex of the regular hexagon, cut the chord from top to bottom; The numb 1 records that triangle connecte the vertices in the center; The sum of squares of a downward triangle is diagonal, which is easy to look up and simplify the proof.