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Mar 10, 2017
 #1
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Perimeter

XZ = sqrt ( 5^2 + 3^2)  = sqrt (34)

XY = sqrt ( 4^2 + 5^2)  = sqrt (41)

YZ = sqrt ( 9^2 + 2^2)  = sqrt (85) 

 

sqrt (34) + sqrt(41) + sqrt (85) ≈  21.45  units.....correct  !!!

 

The area is a little difficult.....there are several ways to do this using trig.....but....I'm going to assume you might not have had that.....so....let's do this

 

The slope between Y(4,-4), and Z(-5,-2)  is (-2 - -4) / (-5 -4)  = 2/-9  = -2/9

 

And the equation of the line joining  these two points  is   y = (-2/9)(x - 4) - 4  →

y = (-2/9x + 8/9 - 4 →  y = (-2/9)x - 28/9

 

So...... a perpendicular line from the apex of the triangle - point X - to this line will serve as the height of the triangle.....and the slope of this perpendicular line will be the negative reciprocal of -2/9   = 9/2

 

And the equation of this line will be

y = (9/2) ( x - 0) + 1   → y =  (9/2)x + 1

 

Setting these lines equal, we can find the x coordinate of their intersection

 

(-2/9)x - 28/9   =  (9/2)x + 1

-28/9 - 1  =  (9/2 + 2/9)x

-37/9   = (85/18)x     multiply both sides by 18/85

(-37/9)(18/85)  =  -74/85

 

And the y coordinate of their intersection can be found  as  (9/2)(-74/85) + 1  = -248/85

 

So the distance from X -(0,1)- to  (-74/85, -248/85)  is given by

 

sqrt [ (74/85)^2 + ( 1 + 248/85)^2 ]  = 37/ sqrt (85)  = the triangle's  height

 

So.....the area of a triangle is (1/2) B * H  

The Base is YZ   = sqrt (85)....so the area =

(1/2)sqrt(85) * 37 / sqrt (85)   -  (1/2)(37)  = 18.5 square units  !!!

 

Whew!!!!....that was a lot of work......but....I verified the answer here :

http://www.wolframalpha.com/input/?i=area+triangle+%5B+(0,1),+(4,-4),++(-5,-2)%5D

 

Hope that helps !!!

 

 

cool cool cool

Mar 10, 2017
 #2
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Mar 10, 2017
 #1
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Mar 10, 2017
 #1
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Mar 10, 2017
 #1
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Mar 10, 2017

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