A circle has center (a,0), a is greater than 0 and radius 4 units.
(a) What is the equation of this circle?
(b) Show that if y=x is a tangent to this circle then a=4√2

Question

A circle has center (a,0), a is greater than 0 and radius 4 units. 
(a) What is the equation of this circle?
(b) Show that if y=x is a tangent to this circle then a=4√2

anonymous · Answer

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lalaly · Answer

$$(x-a)^2+y^2=16$$

lalaly · Answer

thats (a)

anonymous · Answer

can ou show me how you got that?

lalaly · Answer

if u have a circle with center (h,k) and radius r
equation of circle is
$$(x-h)^2+(y-k)^2=r^2$$

anonymous · Answer

i got as far as the equation is (x-4)^2+y^2=16

lalaly · Answer

why 4?

lalaly · Answer

the center is (a,0)

anonymous · Answer

but the drawing, i guessed a would be 4

anonymous · Answer

or -4, i honestly guessed though

lalaly · Answer

no it a
x-a

anonymous · Answer

so what would the answers be?

anonymous · Answer

and also how?

anonymous · Answer

lanas right...

lalaly · Answer

$$(x-a)^2+x^2=1$$
try solving this tofind a

lalaly · Answer

=16

lalaly · Answer

if u cnt do it ill do it fr u, but everytime i answer the page freezes

anonymous · Answer

The equation of a circle:
$$(x-a)^{2}+(y-b)^{2}=r^{2}$$ where (a,b) is your center. In this case (a,0) is your circle.
Plug a in for a, and 0 in for b, and the radius in for r
$$(x-a)^{2}+(y-0)^{2}=4^{2} = (x-a)^{2}+(y)^{2}=16$$

lalaly · Answer

http://www.wolframalpha.com/input/?i=%28x-a%29^2%2Bx^2%3D16 frm my equaion the answer is right $$a=4\sqrt2$$

anonymous · Answer

a=4√2 is a given in this, im looking for x and y, seeing as how y=x is a tangent to the circle