What is the magnitude of the resultant vector a and b shown below?

SECOND OPTION.

Step-by-step explanation:

It is important to remember that, by definition, the "Resultant vector " is the vector obtained by adding two or more vectors.

 For this exercise you need to use the formula for calculate the magnitude of the resultant vector obtained by adding the vectors "a" and "b" shown in the picture attached:

Where "c" is the magnitude of the resultant vector asked in the exercise.

You need to analyze the graph given in the exercise.

You can identify that:

Then the next step, knowing which are "a" and "b", is to substitute values into the formula given at the beginning of this explanation, as following:

Finally, evaluating, you get that "c" is: