bawuyi
幼苗
共回答了25个问题采纳率:72% 举报
sina=-2cosa
sina+2cosa=0
sin^2a+4sina*cosa+4cos^2a=0
1.25sin^2a+5sina*cosa+5cos^2a=0
sin^2a+5sina*cosa+2cos^2a
=(1.25sin^2a+5sina*cosa+5cos^2a)-0.25sin^2a-3cos^2a
=-0.25sin^2a-3cos^2a
sina=-2cosa
sin^2a=4cos^2a
sin^2a+cos^2a=1
sin^2a=0.8,cos^2a=0.2
sin^2a+5sina*cosa+2cos^2a
=-0.25sin^2a-3cos^2a
=-0.8
1年前
5