WB JEE 2018 | Vector Algebra Question 3 | Physics

WB JEE 2018

MCQ (Single Correct Answer)

-0.25

In a triangle ABC, the sides AB and AC are represented by the vectors $$3\widehat i + \widehat j + \widehat k$$ and $$\widehat i + 2\widehat j + \widehat k$$, respectively. Calculate the angle $$\angle ABC$$.

$${\cos ^{ - 1}}\sqrt {{5 \over {11}}} $$

$${\cos ^{ - 1}}\sqrt {{6 \over {11}}} $$

$$\left( {90^\circ - {{\cos }^{ - 1}}\sqrt {{5 \over {11}}} } \right)$$

$$\left( {180^\circ - {{\cos }^{ - 1}}\sqrt {{5 \over {11}}} } \right)$$

WB JEE 2017

MCQ (Single Correct Answer)

-0.25

Three vectors $$\overrightarrow A $$ = a$$\widehat i$$ + $$\widehat j$$ + $$\widehat k$$; $$\overrightarrow B $$ = $$\widehat i$$ + b$$\widehat j$$ + $$\widehat k$$ and $$\overrightarrow C $$ = $$\widehat i$$ + $$\widehat j$$ + c$$\widehat k$$ are mutually perpendicular ($$\widehat i$$, $$\widehat j$$ and k are unit vectors along X, Y and Z-axes respectively). The respective values of a, b and c are

0, 0, 0

$$ - {1 \over 2}$$, $$ - {1 \over 2}$$, $$ - {1 \over 2}$$

1, $$-$$1, 1

$${1 \over 2}$$, $${1 \over 2}$$, $${1 \over 2}$$

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