文科高数定积分的计算求解谢谢 20
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(1). ∫<π/3,π>cos(x+π/3)dx= ∫<π/3,π>cos(x+π/3)d(x+π/3)
=sin(x+π/3)∣<π/3,π>=sin(π+π/3)-sin(π/3+π/3)
=-sin(π/3)-sin(2π/3)=-sin(π/3)-sin(π-π/3)=-sin(π/3)-sin(π/3)
=-2sin(π/3)=-√3;
(2).∫<0,π/4>[2/(1+x²)]dx=2arctanx∣<0,π/4>=2arctan(π/4);
=sin(x+π/3)∣<π/3,π>=sin(π+π/3)-sin(π/3+π/3)
=-sin(π/3)-sin(2π/3)=-sin(π/3)-sin(π-π/3)=-sin(π/3)-sin(π/3)
=-2sin(π/3)=-√3;
(2).∫<0,π/4>[2/(1+x²)]dx=2arctanx∣<0,π/4>=2arctan(π/4);
追问
请问为什么arctanπ/4等于1?
追答
arctanπ/4≠1;
tan(π/4)=1,arctan1=π/4;
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