Terence yau asked in 科學及數學數學 · 1 decade ago

straight line

Two lines pass through (4,3) and each line makes an angle 45°with the line y=1/3x. find the equations of the two lines.

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  • 1 decade ago
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    設L:y=mx+c

    tan45°=∣(m-1/3) / [1+m/3] ∣

    ±1= (3m-1) / (3+m) [[[(右邊分子分母乘3)]]]

    3+m=3m-1 or -3-m=3m-1

    2m=4 or 4m=-2

    m=2 or -1/2

    ∴y=2x+c and

    y=-1/2+c

    put(4,3)

    3=2(4)+c , 3=-1/2(4)+c

    c=-5 , c=5

    two lines

    y=2x-5

    y=-1/2+5

    Source(s): me
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