Animated Solution for Mathematics - Differentiation: The shortest distance between the line x−y=1 and the curve x2=2y is:
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Visualized Solution
Visualizing the Problem
Given Curve: x2=2y (Parabola)
Given Line: x−y=1 (Straight Line)
Objective: Find the shortest distance between them.
The Shortest Distance Principle
Key Concept: The shortest distance occurs along the common normal.
The tangent at the closest point on the curve is parallel to the given line.
Therefore: Slope of tangent=Slope of line.
Finding the Curve's Slope Function
Differentiating x2=2y with respect to x:
dxd(x2)=dxd(2y)
Differentiating the Parabola
2x=2dxdy
dxdy=x
Identifying the Line's Slope
Line Equation: x−y=1⇒y=x−1
Comparing with y=mx+c:
Slope of the line (mL) = 1
Setting the Tangency Condition
Condition for shortest distance: dxdy=mL
Substituting the values:
x=1
Finding the Y-coordinate
Substitute x=1 into x2=2y:
(1)2=2y
1=2y⇒y=21
Closest Point P(1,21)
Recalling the Distance Formula
Point P(1,21)
Line: x−y−1=0 (where a=1,b=−1,c=−1)
Distance Formula: d=a2+b2∣ax1+by1+c∣
Substituting into the Distance Formula
Substituting into the formula:
d=(1)2+(−1)2∣(1)(1)+(−1)(21)+(−1)∣
Simplifying the Numerator
Numerator: ∣1−21−1∣
=∣−21∣
=21
Calculating the Denominator
Denominator: 12+(−1)2
=1+1=2
Final Result
Final Distance d=221
d=221
Final Answer:221
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The Sigma Insight: Tangents, Normals and Rate Measure
Solution Diagram
Analyzing the Setup
To find the shortest distance between the parabola x2=2y and the line x−y=1, we utilize the geometric principle that the shortest distance occurs at the point where the tangent to the parabola is parallel to the given line.
First, we determine the slope of the line x−y=1. Rearranging this into slope-intercept form, we get y=x−1, which indicates that the slope m is 1.
Finding the Point of Tangency
For the parabola x2=2y, we differentiate with respect to x to find the slope of the tangent at any arbitrary point. Differentiating both sides yields:
2x=2dxdy
This simplifies to the slope function:
dxdy=x
Since the tangent must be parallel to the line, we set the slope of the tangent equal to the slope of the line:
x=1
This value represents the x-coordinate of the point on the parabola closest to the line. Substituting x=1 back into the parabola equation x2=2y, we find:
(1)2=2y⇒y=21
Thus, the point of closest approach is P(1,21).
Final Calculation
We now calculate the perpendicular distance from point P(1,21) to the line x−y−1=0 using the distance formula:
d=a2+b2∣ax1+by1+c∣
Substituting the values a=1, b=−1, c=−1, x1=1, and y1=21:
d=(1)2+(−1)2∣(1)(1)+(−1)(21)+(−1)∣
Simplifying the numerator:
∣1−21−1∣=∣−21∣=21
The denominator is 1+1=2. Therefore, the shortest distance is: