IDNStudy.com, ang iyong gabay para sa mga sagot ng komunidad at eksperto. Hanapin ang mga solusyong kailangan mo nang mabilis at tiyak sa tulong ng aming mga bihasang miyembro.

find the equation of a circle passing through (3,7) and tangent to the lines x-3y+8=0 and y=3x

Sagot :

Lines tangent:
x-3y+8=0
y=3x

Simply substitute the values:
x-3(3x)+8=0
x-9x+8=0
-8x+8=0
Subtract both sides by 8
-8x=-8
Divide both sides by -8
x=1

Substitute the value of x:
y=3(1)
y=3

The coordinate is: (1,3) which is where it is tangent..

Both of them are endpoints of the circle so I recommend you draw a line connecting both of them, then attach, then the midpoint of it should be the center

M:((1+3)/2 , (3+7)/2)
M:(4/2 , 10/2)
M:(2,5)

Find the distance from the radius to one of its endpoints..
d=√[(x2-x1)²+(y2-y1)²]
d=√[(3-2)²+(7-5)²]
d=√[1+4]
d=√5

The center is (2,5) Now 2 is the h and 5 is the k from the equation:
(x-h)²+(y-k)²=r²
(x-2)²+(y-5)²=(√5)²
x²-4x+4+y²-10y+25=5
x²-4x+y²-10y+24=0

Hope this helps =)