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Mathematics

Given that A(5, 4), B(–3, –2) and C(1, –8) are the vertices of a ΔABC. Find:

(i) the slope of median AD

(ii) the slope of altitude BM

Straight Line Eq

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Answer

(i) Since, AD is median. So, D is the mid-point of BC.

By using formula,

(x, y) = (x1+x22,y1+y22)\Big(\dfrac{x1 + x2}{2}, \dfrac{y1 + y2}{2}\Big)

Substitute values we get,

D = (3+12,2+(8)2)=(22,102)=(1,5)\Big(\dfrac{-3 + 1}{2}, \dfrac{-2 + (-8)}{2}\Big) = \Big(\dfrac{-2}{2}, \dfrac{-10}{2}\Big) = (-1, -5)

By using slope formula,

m = y2y1x2x1\dfrac{y2 - y1}{x2 - x1}

Slope of AD = 5415=96=32\dfrac{-5 - 4}{-1 - 5} = \dfrac{-9}{-6} = \dfrac{3}{2}

Hence, slope of the median AD = 32\dfrac{3}{2}.

(ii) The altitude BM is perpendicular to the side AC. Therefore, the product of their slopes is -1.

Slope of AC = 8415=124=3\dfrac{-8 - 4}{1 - 5} = \dfrac{-12}{-4} = 3

mBM × 3 = -1

mBM = 13\dfrac{-1}{3}

Hence, slope of the BM = 13-\dfrac{1}{3}.

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