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# C4 parametric equations watch

1. Hi everyone, could someone explain the best way to go about this question to me please? I'm sure I'm missing something obvious but I just can't work it out

parametric equations:

i) Find the points of intersection with the axis (I can do this part)
ii) Find the coordinates of the points for which the tangent to the curve cuts the x-axis at (4, 0).

How would I do part ii?

2. (Original post by kingkong95)
Hi everyone, could someone explain the best way to go about this question to me please? I'm sure I'm missing something obvious but I just can't work it out

parametric equations:

i) Find the points of intersection with the axis (I can do this part)
ii) Find the coordinates of the points for which the tangent to the curve cuts the x-axis at (4, 0).

How would I do part ii?

I haven't tried it, but I think the first step would be to find a general equation for the tangent to the curve at a point described by parameter t.
3. (Original post by kingkong95)
Hi everyone, could someone explain the best way to go about this question to me please? I'm sure I'm missing something obvious but I just can't work it out

parametric equations:

i) Find the points of intersection with the axis (I can do this part)
ii) Find the coordinates of the points for which the tangent to the curve cuts the x-axis at (4, 0).

How would I do part ii?

From the parametric equations

The equation of tangent line is

Solve these equations simultaneously substituting the 2nd into the first one
You vill get a quadratic equation for x with parameter of m.
Consider that for x you can get only one solution because the line has
one common point with the curve (ellipse).
So in the formula for the quadratic equation the discriminant D=0
From this equation you will get the value of m
then finish the solution or find the point where the derivative is m
4. (Original post by davros)
I haven't tried it, but I think the first step would be to find a general equation for the tangent to the curve at a point described by parameter t.
(Original post by ztibor)
From the parametric equations

The equation of tangent line is

Solve these equations simultaneously substituting the 2nd into the first one
You vill get a quadratic equation for x with parameter of m.
Consider that for x you can get only one solution because the line has
one common point with the curve (ellipse).
So in the formula for the quadratic equation the discriminant D=0
From this equation you will get the value of m
then finish the solution or find the point where the derivative is m
Thanks for the help! I'll try it now

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