What are its direction cosines, taken in the…

What are its direction cosines, taken in the direction from A to B?

Question 45

MediumOriginal question

A line passes through $A(2, -1, 3)$ and $B(4, 3, -1)$ .

What are its direction cosines, taken in the direction from $A$ to $B$ ?

\frac{1}{3}, \frac{2}{3}, \frac{2}{3}

Correct answerYour answer

\frac{1}{5}, \frac{2}{5}, -\frac{2}{5}

Correct answerYour answer

-\frac{1}{3}, -\frac{2}{3}, \frac{2}{3}

Correct answerYour answer

\frac{1}{3}, \frac{2}{3}, -\frac{2}{3}

Correct answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer D

Correct answer: D

$\sqrt{4 + 16 + 16} = 6$ .
$\frac{2}{6}, \frac{4}{6}, -\frac{4}{6} = \frac{1}{3}, \frac{2}{3}, -\frac{2}{3}$ .

Worth noting

$\frac{1}{5}, \frac{2}{5}, -\frac{2}{5}$ divides by $2 + 4 + 4 = 10$ , not by the length 6.

Ten questions from Three-Dimensional Geometry, at your own pace.

Ten questions from Three-Dimensional Geometry, at your own pace.