已知tanx=2,求下列各式的值,(1) sinxcosx(2) 2sin^2x-3sinxcosx-4cos^2x
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![已知tanx=2,求下列各式的值,(1) sinxcosx(2) 2sin^2x-3sinxcosx-4cos^2x](/uploads/image/z/2093330-2-0.jpg?t=%E5%B7%B2%E7%9F%A5tanx%3D2%2C%E6%B1%82%E4%B8%8B%E5%88%97%E5%90%84%E5%BC%8F%E7%9A%84%E5%80%BC%2C%281%29+sinxcosx%282%29+2sin%5E2x-3sinxcosx-4cos%5E2x)
已知tanx=2,求下列各式的值,(1) sinxcosx(2) 2sin^2x-3sinxcosx-4cos^2x
已知tanx=2,求下列各式的值,(1) sinxcosx(2) 2sin^2x-3sinxcosx-4cos^2x
已知tanx=2,求下列各式的值,(1) sinxcosx(2) 2sin^2x-3sinxcosx-4cos^2x
sin2x=(2tanx)/(1+tan^2x)=4/5
(1)sinxcosx=1/2sin2x=2/5
(2)(2sin^2x-3sinxcosx-4cos^2x )/(sinxcosx)=2tanx-3-4cotx=-1
2sin^2x-3sinxcosx-4cos^2x =-sinxcosx=-2/5