Question Details

Options

A

7/10 unit

B

10 unit

C

0 unit

D

34/√1045 unit

Correct Answer :

34/√1045 unit

Solution :

The correct option is 34/√1045 unit.

To find the shortest distance between two skew lines in three-dimensional space, we can analyze the equations of the lines from the provided images:
Line 1:

x 1 2 = y + 1 4 = z 1 3

From this equation, we identify a point on Line 1 as:
a 1 = i ^ j ^ + k ^
And its direction vector as:
n 1 = 2 i ^ + 4 j ^ + 3 k ^

Line 2:
The given equation is:

2 x 1 5 = y 2 3 = z 6

To write Line 2 in standard symmetric form, we divide the numerator and denominator of the first term by 2:
x 1 2 5 2 = y 2 3 = z 6

From this standard form, we identify a point on Line 2 as:
a 2 = 1 2 i ^ + 2 j ^ + 0 k ^
And its direction vector as:
n 2 = 5 2 i ^ + 3 j ^ + 6 k ^

Step 1: Calculate the difference vector between the two points
Subtracting the position vector of the point on the second line from the first:
a 1 a 2 = 1 1 2 i ^ + 1 2 j ^ + 1 0 k ^
a 1 a 2 = 1 2 i ^ 3 j ^ + k ^

Step 2: Find the cross product of the direction vectors
The vector normal to both lines is given by the cross product:
n 1 × n 2 = | i ^ j ^ k ^ 2 4 3 5 2 3 6 |
Expanding this determinant along the first row:
n 1 × n 2 = i ^ 4 × 6 3 × 3 j ^ 2 × 6 3 × 5 2 + k ^ 2 × 3 4 × 5 2
n 1 × n 2 = i ^ 24 9 j ^ 12 15 2 + k ^ 6 10
n 1 × n 2 = 15 i ^ 9 2 j ^ 4 k ^

Step 3: Calculate the magnitude of the cross product vector
| n 1 × n 2 | = 15 2 + ( 9 2 ) 2 + ( 4 ) 2
| n 1 × n 2 | = 225 + 81 4 + 16 = 241 + 81 4
Finding the common denominator:
| n 1 × n 2 | = 964 + 81 4 = 1045 4 = 1045 2

Step 4: Find the dot product of the difference vector and the cross product vector
a 1 a 2 n 1 × n 2 = 1 2 15 + 3 9 2 + 1 4
= 15 2 + 27 2 4 = 42 2 4 = 21 4 = 17

Step 5: Apply the shortest distance formula
The shortest distance d is given by:
d = | a 1 a 2 n 1 × n 2 | n 1 × n 2 | |
Substituting the calculated values:
d = 17 1045 2 = 34 1045  unit

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