Answer :
First resolve the 513N thrust into two components of the right angles.
In the forward side, we have 513N cos(32.4°)
At right angles, we have 513N sin(32.4°)
So...
513N cos(32.4°) = 433.14 N
513N sin(32.4°) = 274.88 N
Next get the total forward force of the rocket.
725 N + 433.14 N = 1,158.14 N
And the total force at right angles:
0 + 274.88 N = 274.88 N
Next solve the Resultant Magnitude (F) through Pythagorean theorem.
F² = a² + b²
F² = (1158.14 N)² + (274.88 N)²
F² = 1,341,288.26 + 75,559.01
F² = 1,416,847.27
F = √1,416,847.27
F = 1,190.3139
F = 1,190.31
Now that we have resultant magnitude, find the direction by dividing total force exerted at right angles by the total force exerted at the forward side.
tanC = 274.88 N / 1,158.14 N
tanC = 0.237346089419241
C = tan⁻¹ 0.237346089419241
C = 13.35°