Download App

VECTOR ALGEBRA — Maths STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceMathsVECTOR ALGEBRA1 Mark
MCQ
If $\vec{\text{a}},\vec{\text{b}},\vec{\text{c}} $ are three non-coplanar mutually perpendicular unit vectors, then $\big[\vec{\text{a}}\vec{\text{b}}\vec{\text{c}}\big],$ is:
  • ✓
    $\pm 1$
  • B
    $0$
  • C
    $-2$
  • D
    $2$
✓

Answer

Correct option: A.
$\pm 1$
We have
$\big[\vec{\text{a}}\vec{\text{b}}\vec{\text{c}}\big]$
$=\big(\vec{\text{a}}\times\vec{\text{b}}\big).\vec{\text{c}}$
$=\big|\vec{\text{a}}\times\vec{\text{b}}\big|\big|\vec{\text{c}}\big|\cos0^\circ$ or $\big|\vec{\text{a}}\times{\vec{\text{b}}}\big|\big|\vec{\text{c}}\big|\cos180^\circ$ $\big(\therefore\vec{\text{a}},\vec{\text{b}},\vec{\text{c}}$ are perpendicular to each other$)$
$=\big|\vec{\text{a}}\times\vec{\text{b}}\big|$ or $-\big|\vec{\text{a}}\times\vec{\text{b}}\big|$ $\big(\therefore\big|\vec{\text{c}}\big|=1,\cos0^\circ=1\text{ and }\cos180^\circ=-1\big)$ $$
$=\big|\vec{\text{a}}\big|\big|\vec{\text{b}}\big|\sin90^\circ$ or $-\big|\text{a}\big|\big|\vec{\text{b}}\big|\sin90$ $\big(\therefore\vec{\text{a}} \text{ is perpendicular to }\vec{\text{b}})$
$=1 \text{ or }-1$ $\big(\therefore\big|\vec{\text{a}}\big|=1 \text{ and }\big|\vec{\text{b}}\big|=1\big)$ $$
$=\pm1$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "M.C.Q (1 Marks)" from VECTOR ALGEBRA→VECTOR ALGEBRA — all question types→Maths STD 12 Science question papers→Gujarat Board STD 12 Science question papers→Gujarat Board question paper generator→

Similar questions

Side of an equilateral triangle expands at the rate of $2\text{ cm}/ \text{sec}.$ The rate of increase of its area when each side is $10\ cm$ is :
→
The Convex Polygon Theorem states that the optimum (maximum or minimum) solution of a LPP is attained at atleastone of the ______ of the convex set over which the solution is feasible.
→
A unit vector perpendicular to vector  $  c $ and coplanar with vectors  $a$  and $b$ is
→
$2\tan^{-1}\big\{\text{cosec}\big(\tan^{-1}\text{x}\big)-\tan\big(\cot^{-1}\text{x}\big)\big\}$ is equal to:
→
In which of the function is one-one defined in $R \rightarrow$ R .
→
If $\text{f(x)}=\frac{1}{1-\text{x}},$ then the set of points discontinuity of the function f(f(f(x))) is:
→
The value of $\int_{\pi /4}^{3\pi /4} {\frac{\phi  }{{1 + \sin \phi  }}\,d\phi   ,} $ is
→
$\mathop {\lim }\limits_{n \to \infty } \frac{1}{{{1^3} + {n^3}}} + \frac{4}{{{2^3} + {n^3}}} + .... + \frac{1}{{2n}}$ is equal to
→
$\int_{}^{} {\frac{{x{e^x}}}{{{{(1 + x)}^2}}}dx = } $
→
An ordinary dice is rolled for a certain number of times. If the probability of getting an odd number $2$ times is equal to the probability of getting an even number $3$ times, then the probability of getting an odd number for odd number of times is
→