1. ## vector help

Three vectors a, b and c are each 50m long and lie in the x-y place. Their directions relative to the positive x axis are 30 degree, 195 degree and 315 degree respectively. what are the magnitude and angle of a + b + c, and of a - b + c. What are the magnitude and angle of a fourth vector d such that (a + b) - (c + d) = 0.

I took the angle between the two vectors a and b as 195 - 30 = 165 and tried to apply parallelogram law of addition for a and b. and c could be added to a + b.

Is the method correct? The problem is I am not able to do anything with the angle 165 degree.

How to do this problem. Any help?

2. ## Re: vector help

Not sure that you can find the sum of the vectors using the parallelogram law (someone may correct me). I would find the x,y components of the vectors and then do simple vector addition. So for a you have an angle of 30 and a hypotenuse of 50. Use plain old trig to get x and y. Do the same for the others.

3. ## Re: vector help

ok. For 30 degree, it would be easy. What about 195 degree and 315 degree?

4. ## Re: vector help

Well 195 gives you a triangle with an angle of 15 from the horizontal. You should be able to figure out the x,y components.