2.L2 = π θ/45 (a-cc/sin θ) (b→ 0，c = √ (a 2-b 2)，θ= arccos((a-b)/a) 1. 1)。

3. First derivative:-10/(n+5) 2+8/(n+4) 2.

4. Second derivative: 10*2! /(n+5)^3-8*2！ /(n+4)^3。

5.n-order derivative formula: (-1) n * n! *[ 10/(n+5)^(n+ 1)-8/(n+4)^(n+ 1)]。

6.l 1=πqn/arctgn(b→a, q = ab, n = ((a-b)/a) 2,) This is derived from the principle of circle length, and its accuracy is average.

7、(tanx)'=(secx)^2

(secx)'=secxtanx

(cotx)'=-(cscx)^2

(cscx)'=-csxcotx

(arcsinx)'= 1/√( 1-x^2)

(arccosx)'=- 1/√( 1-x^2)。

8、(arctanx)'= 1/( 1+x^2)

(arccotx)'=- 1/( 1+x^2)

(shx)'=chx

(chx)'=shx

(uv)'=uv'+u'v

(u+v)'=u'+v '

(u/)'=(u'v-uv')/^2。