Question

8.If a, b,y are the direction angles of a vector, then which the following can be
a+ß?
(a) 80°
(b) 60°
(c) 120°
(d) Can't be determined.
​

Answer 1

The value of a+ß -

(d) Can't be determined.

​Direction angle of a vector:

• A vector represented by (a,b,c) in three-dimentional space, having direction cosines of this vector as -

1. $cos\alpha = \frac{a} \sqrt{a^{2}+ b^{2} +c^{2} } }$
2. $cos\beta = \frac{b} \sqrt{a^{2}+ b^{2} +c^{2} } }$
3. $cos\pi = \frac{c} \sqrt{a^{2}+ b^{2} +c^{2} } }$

• The direction angles, are the angles that the vector makes with respect to the positive X, Y and Z axes.
• Mathematically the direction cosines are determined rather than the direction angles.
• Both direction consines and angles cannot be determined without preconstraints.