A triangle has corners A, B, and C located at (2 ,9 )(2,9), (1 ,4 )(1,4), and (6 , 5 )(6,5), respectively. What are the endpoints and length of the altitude going through corner C?

1 Answer
Jan 27, 2017

The endpoints are (18/13,77/13)(1813,7713) and (6,5)(6,5) and length of the altitude going through corner C is 4.7074.707

Explanation:

The slope of line ABAB is (4-9)/(1-2)=(-5)/(-1)=54912=51=5 and equation of ABAB is (y-4)=5(x-1)(y4)=5(x1)

i.e. 5x-y=15xy=1 ................................(1)

Hence if CD_|_ABCDAB, with DD on ABAB, slope of CDCD will be (-1)/5=-1/515=15

and equation of CDCD is (y-5)=-1/5(x-6)(y5)=15(x6)

or 5y-25=-x+65y25=x+6 i.e. x+5y=31x+5y=31 ................................(2)

Solving (1) and (2) gives us the coordinates of DD. For tis putting y=5x-1y=5x1 from (1) in (2) gives

x+25x-5=31x+25x5=31 or 26x=3626x=36 i.e. x=36/26=18/13x=3626=1813

and hence y=5xx18/13-1=77/13y=5×18131=7713

and coordinated of DD are (18/13,77/13)(1813,7713)

and CD=sqrt((6-18/13)^2+(5-77/13)^2)CD=(61813)2+(57713)2

= sqrt((60/13)^2+(-12/13)^2)(6013)2+(1213)2

= 1/13sqrt(3600+144)=sqrt3744/13=61.188/13=4.7071133600+144=374413=61.18813=4.707
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