∫（0→π/2）(cosx)^5·(sinx)²dx
=∫（0→π/2）(cosx)^4·(sinx)²d(sinx)
=∫（0→π/2）(1-sin²x)²·(sinx)²d(sinx)
=∫（0→π/2）[(sinx)^6+2(sinx)^4+(sinx)^2]d(sinx)
=[1/3(sinx)^3-2/5(sinx)^5+1/7(sinx)^7] |（0→π/2）
=1/3-2/5+1/4
=8/105