document.write( "Question 864960: I previously asked this question and got this solution (after question). But I would appreciate further clarification.
\n" ); document.write( "The line with the equation y=mx is tangent to the circle with centre (-8,0) and radius 4 at the point P(x,y). 
\n" ); document.write( "a)find x coordinate of P in terms of m 
\n" ); document.write( "b)Show that m = +- sqrt (3)/ 3 and hence find the coordinates of P
\n" ); document.write( "(x+8)^2+y^2=16
\n" ); document.write( "(x+8)^2+y^2=16, y=mx
\n" ); document.write( "m = 1/sqrt(3),   x = -6,   y = m x
\n" ); document.write( "m =-1/sqrt(3),   x = -6,   y = m x
\n" ); document.write( "+-1/sqrt(3)=+-sqrt(3)x/3
\n" ); document.write( "y=+-sqrt(3)x/3
\n" ); document.write( "x=-6,   y =2sqrt(3)
\n" ); document.write( "P=(-6,2sqrt(3))
\n" ); document.write( "Can you please provide further clarification- 
\n" ); document.write( "Step 3 and 4-
\n" ); document.write( "m = 1/sqrt(3), x = -6, y = m x 
\n" ); document.write( "m =-1/sqrt(3), x = -6, y = m x 
\n" ); document.write( "How was the x coordinate found. 
\n" ); document.write( "Step 5 
\n" ); document.write( "+-1/sqrt(3)=+-sqrt(3)x/3 
\n" ); document.write( "what is happening here for one to become the other.\r
\n" ); document.write( "\n" ); document.write( "I need this explained very simply So i i can understand it. Especially my queries about the steps. Thank you very much.\r
\n" ); document.write( "\n" ); document.write( "
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Algebra.Com's Answer #521431 by KMST(5328)\"\" \"About 
You can put this solution on YOUR website!
I see several ways to get the answer. I cannot tell if one of the ways I would use was used in the first answer you got. Maybe the reasoning was through a different way. I can explain one or more ways. However, I am a long-winded explainer, so you may get more explanation that you bargained for.
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\n" ); document.write( "USING GEOMETRY AND ANALYTIC GEOMETRY:
\n" ); document.write( "The tangent to a circle is perpendicular to the radius at the point of tangency, so I would draw the sketch like this:
\n" ); document.write( " The tangents, radii, and the x-axis form right triangles OPC and OQC.
\n" ); document.write( "The two triangles are congruent, with P(x,y) and Q(x,-y), so I only need to solve OPC.
\n" ); document.write( "I know that the length of leg CP is \"4\", and the hypotenuse OC is \"8\" .
\n" ); document.write( "\"sin%28theta%29=4%2F8=1%2F2\"
\n" ); document.write( "That tells me that the angle \"theta\" measures \"30%5Eo\"
\n" ); document.write( "and OPC is a 30-60-90 triangle.
\n" ); document.write( "From the tangent of that \"30%5Eo\" angle you can also get the slopes of the tangents.
\n" ); document.write( " .
\n" ); document.write( "We multiply times \"%28sqrt%283%29%2Fsqrt%283%29%29\" because we do not like to see square roots in denominators,
\n" ); document.write( "so m = +- \"sqrt%283%29%2F3\" .
\n" ); document.write( "Of course, OP is the line with the negative slope, and OQ is the line with the positive slope.
\n" ); document.write( "For OP, \"y=%28-sqrt%283%29%2Fsqrt%283%29%29%29x\" and
\n" ); document.write( "for OQ, \"y=%28sqrt%283%29%2Fsqrt%283%29%29%29x\" .
\n" ); document.write( "The altitude of that right triangle splits it into two similar right triangles, CPM, and OPM.
\n" ); document.write( "As the ratio of short leg to hypotenuse for OPC is \"4%2F8=1%2F2\", the ratio is also the same for CPM, and OPM, so
\n" ); document.write( "\"CM=4%2A%281%2F2%29=2\" and the x-coordinate of points M and P (and Q) is \"-8%2B2=highlight%28-6%29\"
\n" ); document.write( "For OP, \"y=%28-sqrt%283%29%2Fsqrt%283%29%29%29x\"
\n" ); document.write( "and for P, \"y=mx=m%2A%28-6%29=%28sqrt%283%29%2Fsqrt%283%29%29%2A%28-6%29=2sqrt%283%29\" .
\n" ); document.write( "On the other hand, for Q, \"y=-2sqrt%283%29\" .
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\n" ); document.write( "WITHOUT MENTIONING GEOMETRY (too much):
\n" ); document.write( "OK, we need to know the equation of the circle, and I could call that analytical geometry, but you learn that in algebra 2 too.
\n" ); document.write( "The equation of a circle with radius \"r\" and center at \"%22%28+h+%2C+k+%29%22\" is
\n" ); document.write( "\"%28x-h%29%5E2%2B%28y-k%29%5E2=r%5E2\" .
\n" ); document.write( "For the circle in your problem, that would be
\n" ); document.write( "\"%28x-%28-8%29%29%5E2%2B%28y-0%29%5E2=4%5E2\" ---> \"%28x%2B8%29%5E2%2By%5E2=16\" ---> \"x%5E2%2B16x%2B64%2By%5E2=16\"
\n" ); document.write( "If \"y=mx\" is tangent to the circle, there is only one point in common to circle and line,
\n" ); document.write( "so \"system%28x%5E2%2B16x%2B64%2By%5E2=16%2Cy=mx%29\" has one and only one solution.
\n" ); document.write( "\"system%28x%5E2%2B16x%2B64%2By%5E2=16%2Cy=mx%29\"-->\"x%5E2%2B16x%2B64%2B%28mx%29%5E2=16\"-->\"x%5E2%2B16x%2B64%2Bm%5E2x%5E2=16\"-->\"%28m%2B1%29x%5E2%2B16x%2B64-16=0\"-->\"%28m%2B1%29x%5E2%2B16x%2B48=0\"
\n" ); document.write( "For what value of \"m\" would that quadratic equation have one and only one solution?
\n" ); document.write( "A quadratic \"ax%5E2%2Bbx%2Bc=0\" has one and only one real solution when \"b%5E2-4ac=0\" ,
\n" ); document.write( "and then \"x=-b%2F2a\"
\n" ); document.write( "In the case of \"%28m%2B1%29x%5E2%2B16x%2B48=0\" ,
\n" ); document.write( "\"b=16\" , \"a=m%5E2%2B1\" , and \"c=48\" .
\n" ); document.write( "It will have one and only one real solution when
\n" ); document.write( "\"16%5E2-4%2A%28m%5E2%2B1%29%2A48=0\"-->\"16%5E2=4%2A48%2A%28m%5E2%2B1%29\"-->\"16%2A16=4%2A3%2A16%2A%28m%5E2%2B1%29\"-->\"16%2Across%2816%29=4%2A3%2Across%2816%29%2A%28m%5E2%2B1%29\"-->\"16=12%28m%5E2%2B1%29\"
\n" ); document.write( "So \"m%5E2%2B1=16%2F12\"-->\"m%5E2%2B1=4%2F3\"-->\"m%5E2=4%2F3-1\"-->\"m%5E2=1%2F3\"
\n" ); document.write( "m = +-\"sqrt%281%2F3%29\"= +- \"1%2Fsqrt%283%29\"= +- \"sqrt%283%29%2F3\" .
\n" ); document.write( "In either case, we can use \"x=-b%2F2a\" to find the same \"x\" value:
\n" ); document.write( "\"m%5E2%2B1=4%2F3\" --> \"highlight%28x=%28-16%29%2F%28m%5E2%2B1%29%29\"
\n" ); document.write( "That is the \"x coordinate of P in terms of m\" as your problem asked for.
\n" ); document.write( "Maybe this is the way your teacher/book expected you to solve the problem.
\n" ); document.write( "We can calculate further (apparently not required by your problem):
\n" ); document.write( "\"x=-16%2F%28%284%2F3%29%29=-16%2A%283%2F4%29=-6\"
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