Junior high school is mainly an acute trigonometric function, right?

In a right triangle, this picture is a bit big.

Take angle a as an example:

Sine is equal to the hypotenuse of the opposite side; Sina = account

Cosine (cos) is equal to the ratio of adjacent side to hypotenuse; cosA=b/c

Tangent (tan) is equal to the opposite side of the adjacent side; tanA=a/b

Mainly this, this is to be remembered.

In high school, the focus was on expanding the angle to any angle.

As shown by a circle with a radius of 1.

More specifically: r = under the radical sign (x? +y？ )

sinθ= y/r

cosθ= x/r

tanθ= y/x

The trigonometric function in senior high school also introduces the radian system, focusing more on the radian system in the topic. Please refer to the website link of radian system.

You also need to remember the inductive formula, please refer to the webpage link (only know sin cos tan). The inductive formula mainly transforms any angle into an acute trigonometric function.

High school also needs to learn trigonometric identities. Please refer to the web link, just know: basic trigonometric identities,

Sum and difference of two angles, double angle (deformation: power drop formula), Asinα+Bcosα = √(A? +B？ ) sin [α+θ] (where tan θ = b/a), if you want to be higher, you need to master the sum-difference product.