2sinX+3cosX=0,求(sin^2 X+sin2X)/cos^2 X

来源:学生作业帮助网 编辑:作业帮 时间:2024/11/18 15:23:24
2sinX+3cosX=0,求(sin^2 X+sin2X)/cos^2 X
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2sinX+3cosX=0,求(sin^2 X+sin2X)/cos^2 X
2sinX+3cosX=0,求(sin^2 X+sin2X)/cos^2 X

2sinX+3cosX=0,求(sin^2 X+sin2X)/cos^2 X
已知2sinX+3cosX=0,
则(2sinX+3cosX)^2=4sin^2 X+6sin2X+9cos^2 X=0
所以,sin2X=-(2/3)sin^2 X-(3/2)cos^2 X
带入(sin^2 X+sin2X)/cos^2 X有
(sin^2 X+sin2X)/cos^2 X=(1/3)tg^2 X-3/2
而由已知2sinX+3cosX=0得到tgX=-3/2
所以,(sin^2 X+sin2X)/cos^2 X=(1/3)tg^2 X-3/2=3/4-6/4=-3/4