document.write( "Question 389721: Find the x and y coordinates of the pints on x^2 +y^2=16 at which the tangent line are: a)horizontal and b)have a slope of 1 \n" ); document.write( "
Algebra.Com's Answer #276267 by ewatrrr(24785)\"\" \"About 
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document.write( "Hi,         
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document.write( "Note: tangent and radius are perpendicular
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document.write( "Pt(0,0) and Pt(x,y) 
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document.write( "the point where line with m = 1 is tangent: slope of radius segment = -1
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document.write( " m = (y-0)/(x-0)
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document.write( " -1 = y/x
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document.write( " y = -x
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document.write( " x^2 +y^2=16
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document.write( "      y  = sqrt(16-x^2) substituting -x for y
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document.write( "      -x = sqrt(16-x^2)
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document.write( "     x^2 = 16 - x^2
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document.write( "     2x^2 = 16
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document.write( "    x = ± sqrt(8) 
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document.write( "Points of tangency for the two parallel tangents with slope = 1 are
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document.write( " (2.828,-2.828)  and (-2.828,2.828)   
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