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别为 距离 顶点 已知 定点

已知∠ABC=60°,p为∠ABC内一定点,且p点到边AB,AC的距离分别为1,2,着p到顶点B的距离为

jnlyseo998998 jnlyseo998998 发表于2023-04-06 14:34:10 浏览22 评论0

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设P到顶点B的距离为x,∠ABP=a,∠CBP=b

sina=1/x cosa=√(x^2-1)/x

sinb=2/x cosb来自=√(x^2-4)/x

sin∠ABC=sin(a+b)=sin60°=√3/2

sinac360问答osb+cosasinb=√3/2

1/x*√(x^2-4)/x+√(x^2-1)/x*2/x消三官航但销期=√3/2

2√(x^2-4)+4√(x^2-1)=√3x^2

4x^2-16+16x^2-16+16√(x^2-1)(x^2-4)=3x^4

16√(x^2-1)(x^2-4)=3x^4-20x^2+32

256x^4-1280x^2+1024=9x^8+400x^4+1024-120x^6+192介粉坐河x^4-1280x^2

9x^8-120x^6+336x^4=0

3x^4-40x^2+112=0

△=256

x^2=(40±16)/6=28/3或4

战虽道灯作蛋知者歌万迅x=2/3*√21或2(舍去)

所以P到顶点B的距离为2/3*√21