# Vectors vector

1. Jan 24, 2016

### Leelakrishna23

1. The problem statement, all variables and given/known data
If a vector makes 45 degrees and 60 degrees with x-axis and y-axis respectively then the angle it makes with z-axis is equal to

2. Relevant equations

3. The attempt at a solution

2. Jan 24, 2016

### Suraj M

It would easier to help you if you give it a try first

3. Jan 24, 2016

### Leelakrishna23

I've applied the concept of direction cosines to solve it but I couldn't get the answer.

4. Jan 24, 2016

### Suraj M

5. Jan 24, 2016

### Leelakrishna23

6. Jan 24, 2016

### haruspex

That looks like an answer. Do you think it is wrong?

7. Jan 24, 2016

### Leelakrishna23

Actually the answer(60 degrees) is not given in the answer column. So I just wanted to know if it's correct.

8. Jan 24, 2016

### Leelakrishna23

And i didn't get the cos^2 alpha + cos^2 beta + cos^2 gama=1. Can you please explain me?

9. Jan 24, 2016

### Suraj M

You do get 1!
The answer of 60 degrees looks fine to me.

10. Jan 24, 2016

### haruspex

It's just Pythagoras' formula. If a unit vector from the origin makes those angles with the axes, then the cosines are the x, y, z coordinates.

11. Jan 24, 2016

### Leelakrishna23

Much appreciated, thank you.