You are looking for the equilbrant.
Add the three forces, and set to zero.
let one be at zero, one at 70, and the third unknown.
F=0=7 (cos000N+sin000E+cos070N+sin070E) + Fx(cosYYY N+ sinXXXE)
now, sum North forces=0
7N+7cos70+Fxcosxxx=0
Fxcosxxx=-9.39
and, sum East forces=0
7sin70+FxsinXXX=0
Fx*sinXXX=-6.58
divide one equation by the other
tan XXX=6.58/9.39
angxxx=180+35=215
Fx= 6.58/sin215=11.4
Remember, I have used N as 000, then angles measured clockwise.
check my work.
3 stings are attached on a ring. 2 of the strings make 70 degrees angle and each is pulled with 7.0 N . What force must be applied to keep the 3rd string to keep stationary?
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