Help with Combining Vectors: Find Resultant and Angle

[Baby Einstein]

Hey guys, boggled again need some help. And by the way, thanks to everyone who helped out on the last question...much appreciated!

Combine the following two vectors to find the resultant vector.

Vector A = 7.4 units at 30 degrees and Vector B = 11.1 units at 120 degrees

A. Resulant = 13.34 units ; angle = 86.3 degrees
B. Resulant = 18.49 units; angle = 60.0 degrees
C. Resulant = 17.89 units, angle = 48.1 degrees
D. Resulant = 17.89 units; angle = 41.9 degrees


the only thing I can figure is that using the Pythagoryn Therom is that 7.4 and 11.1 comes out to 13.34 but I can't figure the math on how to get the angle to match up. that's asuming that 13.34 is a correct figure

 

[Baby Einstein]

Ok...using a vector calculator at http://hyperphysics.phy-astr.gsu.ed.../vect.html#vec7 I figured out that "A" is the correct answer. So using the Pyth therom is the right way to start

But I still don't know how to do the math on the angle.

 

[Tide]

Find the x and y components of each vector, add them together to find the resultant vector and the ratio of the y to x components of the resultant vector is the tangent of the desired angle.

 

[Alkatran]

The trick with vectors is to see them as triangles. You draw the vectors out (in the correct direction! VERY important!) then put the x and y components on them to form a triangle.

Then you start solving the triangles... add their x and ys respectively and recombine the summed values using pythagoras to get the resultant.

 

[Baby Einstein]

sine Alpha=11.1/13.34=.832 giving Alpha=56.3degrees. Adding vector A's
30degrees to Alpha gives the total angle of 86.3degrees

Thanks again