Edexcel A Level Maths: Pure:復習筆記3.2.5 Radius & Tangent
Radius & Tangent
What is the relationship between tangents and radii?
- A?tangent?is a line that?touches?a circle at a single point but doesn't cut across the circle
- A tangent to a circle is perpendicular to the radius of the circle at the point of intersection
How can I find the equation of the tangent line to a circle at a given point?
- ?STEP 1: Find the gradient of the radius?OP
- STEP 2: Find the gradient of the tangent
- STEP 3: The equation of the tangent is the equation of the line with that gradient that goes through point?P?(see Equation of a Straight Line)
Exam Tip
- If you understand the formula in Step 2 above, you can find the gradient of the tangent without having to find the gradient of the radius first.
Worked Example
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