# Draw the vectors head to tail so they make a triangle

Draw the vectors head to tail so they make a triangle

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Dick
Homework Helper
Start with the first one. Draw the vectors head to tail so they make a triangle. The information they are giving you tells you some sides and angles in the triangle. Use trig.

Ya thats the part I don't know how to do

Because it # 11 it gives you Vector a = 5 cm long (the magnitude I believe) then it says C or the Resultant is also 5.0 cm long and the angle between A and C is 70 degrees I have no idea how to draw that. I'm used to going in the fashion of Vector A (polar or rectangular) + Vector B (polar or rectangular) + C (polar or rectangular) .. = Resultant

or using the unit vector notation... And for these problems would I have to use the laws of sine and cosine or could I just do it with a vector additon method.

Dick
Homework Helper
Look at the second picture here. http://hyperphysics.phy-astr.gsu.edu/hbase/vect.html. Relabel R to C. That's the picture you should have. It's a triangle. Now fix the lengths and angles you match what you have. Looks to me like an isosceles triangle with side A=side C and an angle of 70 degrees between then. I would find the other angles just using that the sum of all of angle of a triangle is 180. Etc. Sure use things like the law of sines and law of cosines. You can't just directly use a vector addition method because you aren't given any components to add.

Ya I always draw triangles just like that

my problem is they only give the magnitude i believe for A and the magnitude for the resultant so how can I know in what direction the triangles should go ?

Dick
Homework Helper
my problem is they only give the magnitude i believe for A and the magnitude for the resultant so how can I know in what direction the triangles should go ?

You don't have to know that. They are only asking you for the magnitude of B and it's relative angles with the other vectors. You can't know anything about say, the orientation of the triangle. They don't give you enough information to determine that.

So would I use the same method to solve the other #'s ? Thanks a million Dick.

CompuChip
Where did the first post go? It just shows dots now... 