(2) 1+(tanα)^2=(secα)^2。

(3) 1+(cotα)^2=(cscα)^2。

To prove the following two formulas, just divide one formula by (sin α) 2 and the second formula by (cos α) 2.

(4) For any non-right triangle, there is always.

tanA+tanB+tanC=tanAtanBtanC .

Reciprocal relationship:

tanα cotα= 1

sinα cscα= 1

cosα secα= 1

Relationship between businesses:

sinα/cosα=tanα=secα/cscα

cosα/sinα=cotα=cscα/secα

Square relation:

sin^2(α)+cos^2(α)= 1

1+tan^2(α)=sec^2(α)

1+cot^2(α)=csc^2(α)

Two commonly used formulas under different conditions

sin^2(α)+cos^2(α)= 1

tanα*cotα= 1

Special formula

(Sina+sinθ)*(Sina-sinθ)= sin(a+θ)* sin(a-θ)

It is proved that: (Sina+sinθ) * (Sina-sinθ) = 2 sincos * 2 cossin.

=sin(a+θ)*sin(a-θ)