How do you find a if given c and 0 (angle) in a right triangle where a is the opposite, c is the hypotenuse, b is adjacent and 0 is the angle in between c and b?

C can be found using pythagoras theorem. c2=a2+b2. Now, b is not given, but we know that cos (theta) = b/c=>b=c*cos (theta). Substituting b in the above relation, c2=a2+c2 (cos (theta)) ^2=>c2=a2 / (1-cos ((theta)) ^2). c is the squareroot of c2. Hence c=sqrt (2 / (1-cos ((theta)) ^2))