设f(χ)为连续函数,证明: (1)∫0πχf(sinχ)dχ=f(sinχ)dχ=πf(sinχ)dχ; (2)∫02π(|sinχ|)dχ=4f(sinχ)dχ.

admin2018-05-17  24

问题 设f(χ)为连续函数,证明:
    (1)∫0πχf(sinχ)dχ=f(sinχ)dχ=πf(sinχ)dχ;
    (2)∫0(|sinχ|)dχ=4f(sinχ)dχ.

选项

答案(1)令I=∫0πχf(sinχ)dχ,则 I=∫0πχf(sinχ)dχ[*]∫π0(π-t)f(sint)(-dt)=∫0π(π-t)f(sint)dt =∫0π(π-χ)f(sinχ)dχ=π∫0πf(sinχ)dχ-∫0πχf(sinχ)dχ=π∫0πf(sinχ)dχ-I, 则I=[*] (2)∫0f(|sinχ|)dχ=∫πf(|sinχ|)dχ=2∫0πf(|sinχ|)dχ =2∫0πf(sinχ)dχ=4[*]f(sinχ)dχ.

解析
转载请注明原文地址:https://kaotiyun.com/show/S5k4777K
0

最新回复(0)