已知a=2,b=3,a与b的夹角为60°,若a+λb与λa+b的夹角为锐角,求实数λ的取值范围
已知a=2,b=3,a与b的夹角为60°,若a+λb与λa+b的夹角为锐角,求实数λ的取值范围
数学人气:585 ℃时间:2019-08-29 05:56:25
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∵a+λb与λa+b的夹角为锐角∴(a+λb)(λa+b)>0λa²+ab+λ²ab+λb²>04λ+ab+λ²ab+9λ>0又a=2,b=3,a与b的夹角为60°∴ab=2×3×cos60°=3∴4λ+3+3λ²+9λ>0∴3λ²+13λ+3>0解得λ>(...
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