2. The secondary orientation of I is 1.

The fifth power of I is i.

The operation formula of imaginary number I: (a+bi) (c+di) = (a c)+(b d) i.

(a+bi)(c+di)=(ac-bd)+(ad+bc)i

(a+bi)/(c+di)=(ac+bd)/(c？ +d？ )+(bc-ad)i/(c？ +d？ )

r 1(isina+cosa)R2(isin b+cosb)= r 1r 2[cos(a+b)+isin(a+b)]

Where a and b are real numbers, b≠0, i? =- 1。

Formulas of trigonometric functions of imaginary number I:

1、sin(a+bi)= sin(a)cos(bi)+sin(bi)cos(a)= sin(a)cosh(b)+isinh(b)cos(a)

2、cos(a-bi)= cos(a)cos(bi)+sin(bi)sin(a)= cos(a)cosh(b)+isinh(b)sin(a)

3、tan(a+bi)=sin(a+bi)/cos(a+bi)

4、cot(a+bi)=cos(a+bi)/sin(a+bi)

5、sec(a+bi)= 1/cos(a+bi)

6、csc(a+bi)= 1/sin(a+bi)