What is the equation of the tangent to the circle at the point ?

Answer and explanation

Correct answer: D.

  1. Step 1: The radius to has gradient , so the tangent, being perpendicular, has gradient .
  2. Step 2: , so .
  3. Step 3: Rearranged: .
Answer
.
Why not the others: : swaps the coordinates. : has the wrong sign on the term. : is the line through the centre and the point, which is the radius, not the tangent.

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