Answer :

Key point: This problem is based on the application of direction cosines.

We know that if α, β, γ are the angles that a line makes with x , y and z axis respectively then cos α , cos β and cos γ are called its direction cosines and,

cos^{2} α + cos^{2} β + cos^{2} γ = 1

Here,

α = 90° , β = 60° and γ = θ

∴ cos^{2} 90° + cos^{2} 60° + cos^{2} θ = 1

⇒ 0 + (1/2)^{2} + cos^{2} θ = 1

∴ cos^{2} θ = 1 – 1/4 = 3/4

⇒ cos θ = ±√(3/4) = ±(√3)/2

∴ θ = 30° or 150°

But θ is acute. So, θ = 30°

Rate this question :

How useful is this solution?

We strive to provide quality solutions. Please rate us to serve you better.

Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Expertsview all courses

Dedicated counsellor for each student

24X7 Doubt Resolution

Daily Report Card

Detailed Performance Evaluation

RELATED QUESTIONS :

Write the directiMathematics - Board Papers

Find the angle beMathematics - Board Papers

Find the coordinaMathematics - Board Papers

Find a vector <spMathematics - Board Papers

If a line makes aMathematics - Board Papers