dshisuis
幼苗
共回答了365个问题 举报
tan^2x=9/16
sin^2x/cos^2x=9/16
9cos^2x=16(1-cos^2x)
25cos^2x=16
cos^2x=16/25
2+sinXcosX-cos^2X
=2sin^2x+2cos^2x+sinxcosx-cos^2x
=2sin^2x+sinxcosx+cos^x
=(2sin^2x+sinxcosx+cos^x)/cos^2x *cos^2x
=(2tan^2x+tanx+1)cos^2x
=-5/4 *16/25
=-4/5
1年前
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