Statics 1-2 Example: Vector addition by triangle construction

An example problem of vector addition using triangle construction

[ajitsaharan]

Sir how you Determine the formula sin a/30=sin 50°/45.023
Is this belongs to class 11th or 12th or high level

[leonardodialamicua]

I didn´t understand how you found the angle of R.
I could just do 90=(b-15)+ R(angle), then isolating R(angle)=24.305 degrees I guess