Pre Cal/Vectors
posted by Joe .
Can someone show the steps involved in figuring out this type of problem?
Given the magnitudes of vectors u and v and the angle Ό between them, find the magnitude of the sum u + v to the
nearest tenth and the angle that the sum vector makes with u to the nearest degree.
/u/= 20, /v/= 86, Ό = 90°
The answer is 88.3 and 77deg but I don't know how to get to this. Thanks in advance

Follow the same method and steps as I showed you in
http://www.jiskha.com/display.cgi?id=1311551145
except this one is easier since it forms a rightangled triangle, and your parallogram is a rectangle.
If the resultant is R, then
R^2 = 20^2 + 86^2
= 7796
R = √7796 = 88.29
Now use the Sine Law again to get the angle between vectors 
X = 20.
Y = 86.
tanA = Y/X = 86/20 = 4.3,
A = 76.9 deg.
R = X / cosA = 20 / cos76.9 = 88.24
OR
R = Y / sinA = 86 / sin76.9 = 88.3
.