How do you write an equation for a circle with diameter has endpoints(-3,4) and (4,-3)?

1 Answer
May 23, 2016

The equation of the circle is:

color(brown)(=>49/2=(x_i-1/2)^2+(y_i-1/2)^2)492=(xi12)2+(yi12)2

Explanation:

The centre will be at the middle of these points so it is the mean value.

Let point 1 be P_1->(x_1,y_1)->(-3,4)P1(x1,y1)(3,4)
Let point 2 be P_2->(x_2,y_2)->(4,-3)P2(x2,y2)(4,3)
Let the centre be P_c->(x_x,y_c)Pc(xx,yc)
Let the radius be rr

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color(blue)("Determine the centre")Determine the centre

Mean for x-> (4+(-3))/2= 1/2 ->x_c4+(3)2=12xc

Mean for y->(4+(-3))/2=1/2->y_c4+(3)2=12yc

color(blue)("Centre "-> (x_c,y_c)->(1/2,1/2))Centre (xc,yc)(12,12)

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color(blue)("Determine the magnitude of the radius")Determine the magnitude of the radius
Using Pythagoras

I chose (x_1,y_1)(x1,y1) to determine the length of rr

r^2=(x_c-x_1)^2+(y_c-y_1)^2r2=(xcx1)2+(ycy1)2

r^2=[1/2-(-3)]^2+[1/2-4]^2r2=[12(3)]2+[124]2

r=sqrt(49/4+49/4) = sqrt(49/2)r=494+494=492

r=7/sqrt(2)r=72

Multiply by 1 but in the form of 1=sqrt(2)/sqrt(2)1=22

color(blue)(r=(7sqrt(2))/2" "->" " r^2=49/2)r=722 r2=492
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color(blue)("Putting it all together")Putting it all together

Let any xx be x_ixi
Let any yy be y_iyi

The equation of this circle is

r^2=(x_i-x_x)^2+(y_i-y_c)^2r2=(xixx)2+(yiyc)2

color(blue)(=>49/2=(x_i-1/2)^2+(y_i-1/2)^2)492=(xi12)2+(yi12)2