the problem is

so to get the value of c I need to use the cosine law w/c gives me the answer of c=34.544

If i substitute this value in getting the value of sinA it will be w/c gives me a wrong answer.

Help me please.

The original given is:

A system cord is knotted at point 0. Determine the angle of the force exerted at cord c. If the mass of the hanging block is A=850g(8.34N) the tension in B=42N (the angle of Cord B is 25 degrees from the X-axis)