严田惠子
幼苗
共回答了21个问题采纳率:100% 举报
f(x)=1/(1+sin^2x)
=1/(3/2-1/2cos2x)
=2/(3-cos2x) (万能公式代换,cos2x=(1-tan^2x)/(1+tan^2x))
=2(1+tan^2x)/(3+3tan^2x-1+tan^2x)
=2sec^2x/(2+4tan^2x)
∫f(x)dx
=∫2sec^2x/(2+4tan^2x)dx
=∫1/(1+2tan^2x)dtanx
=1/2∫1/(1/2+tan^2x)dtanx
=1/2arctan[tanx/(√2/2)]+C
1年前
8