The three ropes in the figure are tied to a small, very light ring. two of these ropes are anchored to walls at right angles with tensions t1 = 20 n and t2 = 60 n. what are the magnitude and direction of the tension vector t3 in the third rope?
correct: your answer is correct. n. ° (below the positive x-axis)

Let t be the angle made by T3 with the x-axis.

 T3 * cos(t) = 20 N ---- (1)
 T3 * sin(t) = 60 N ----- (2)

 Square both equations and add:

T3^2 = 20^2 + 60^2 = 400 + 3600 = 4000
T3 = sqrt(4000) = 63.25 N
 
divide (2) by (1):
tan(t) = 60/20 = 3
t = arctan(3) = 71.57 degrees.

Since the angle clockwise from the x-axis some books may call it a negative angle and say the angle is -71.57 degrees or round it to -71.6 or even -72 degrees.

The answer is frictional force