Final answer:
The magnitude of the resultant vector is 15 cm.
Step-by-step explanation:
To find the magnitude of the resultant vector, we can use the law of cosines. Let's call the two vectors A and B with lengths 7 cm and 13 cm respectively. The angle between these vectors is 65 degrees. According to the law of cosines, the magnitude of the resultant vector R can be calculated as:
R = sqrt(A^2 + B^2 - 2ABcos(theta))
Plugging in the values, we get:
R = sqrt((7 cm)^2 + (13 cm)^2 - 2(7 cm)(13 cm)cos(65 degrees))
Simplifying, we find that R ≈ 15 cm. Therefore, the answer is option B, 15 cm.