Q1 of 177 Page 24

Can a vector have direction angles 45o, 60o, 120o.

We know that, If l, m, n are the direction cosine of a vector and α, β, γ are the direction angle, then –

l = cosα, m = cosβ, n = cosγ


And, l2 + m2 + n2 = 1 …… (i)


∴ l = cos45°, m = cos60°, n = cos120°



Now, substituting l, m, n in equation (i), we get -






⇒ 1 = 1


⇒ L.H.S = R.H.S


∴ A vector can have direction angles 45o, 60o, 120o.


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