The most commonly used formula: sin2 (a) = [1-cos (2a)]/2cos2 (a) = [1+cos (2a)]/2sin (2x) = 2sinx cosx.
These three formulas are the most commonly used in the first step of simplifying trigonometric functions. They are both power formulas and double-angle (half-angle) formulas.
The second step of trigonometric function simplification is to use special angle simplification, such as:
Sinx+cosx = √ 2 (√ 2/2 sinx+√ 2/2 cosx) = √ 2 [cos (∏/4) sinx+sin (∏/4) cosx] = √ 2 sin (x+∏/4) This is what you need to master most.
Sin (a+b) = Sina COSB+ Xhosa SINB SIN (a-b) = Sina COSB- Xhosa SINB COS (a+b) = Xhosa COSB- Sina SINB COS (a-b) = Xhosa COSB+ Sina SINB. Other formulas are derived by the four of them, and these four can certainly! ! If these four fail, then your trigonometric function will never fail. You can deduce all other formulas.
Then there are the sine and cosine values of special angles, which should be mastered and used skillfully. This generality is necessary in the last step of trigonometric function simplification.
As for the minimum positive period, as long as you can simplify the trigonometric function correctly, it should be O difficult.
Then there are images of sine and cosine. You have to be able to draw images first, and then their monotonous interval is also important. This must be included in the trigonometric function test
Dear ~ ~ I suggest you find a tutor or find a college student around you to talk to you, one-on-one, because students with poor foundation only know one and don't know the other, so it's useless to do more questions. To tell the truth, what I'm telling you here is useless and impractical. You'd better find a college student to tutor you several times. There are few knowledge points about trigonometry. You can do it several times and find a better one. .....
Don't memorize! ! ! Have you memorized all these formulas? Remember the basic four formulas, as long as you can deduce other formulas.