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Jorge
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#1
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#1
From differentiation I have learned that the equation of a tangent is
derived from setting the differentiated result to the value of x at
that particular point (the gradient) and then..

is y-y = grad(x - x)

and the normal being perpendicular grad becomes grad * inverse = -1

i.e. 3/4 becomes - 4/3


Now i'm doing circles, and find that in one of the book's examples working out
the equation of the tangent to a circle, they are using the inverse of the
gradient as if it were for a normal.

Am I missing something?

Thank you for your help.

Jorge :hello:
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evariste
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#2
Report 14 years ago
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(Original post by Jorge)
From differentiation I have learned that the equation of a tangent is
derived from setting the differentiated result to the value of x at
that particular point (the gradient) and then..

is y-y = grad(x - x)

and the normal being perpendicular grad becomes grad * inverse = -1

i.e. 3/4 becomes - 4/3


Now i'm doing circles, and find that in one of the book's examples working out
the equation of the tangent to a circle, they are using the inverse of the
gradient as if it were for a normal.

Am I missing something?

Thank you for your help.

Jorge :hello:
tangent meets radius at right angles.
so if tangent meets circle at (x,y)
the line through centre of circle and (x,y) and the tangent line will be perpendicular.
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