Q13 of 138 Page 24

Mark the correct alternative in each of the following:

The values of x for which the angle between is obtuse and the angle between and the z-axis is acute and less than π/6 are


Here, angle between and is obtuse


So,


⇒ 14x2 – 8x + x ≤ 0


⇒ 14x2 – 7x ≤ 0


⇒ 2x2 – x ≤ 0


⇒ x(2x – 1)≤ 0



or __________(1)


Now, angle between and Z-axis is acute


So,


⇒x≥0 ___________(2)


∴ From (1) and (2) .

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