Complete Question
The complete question is shown on the first uploaded image
Answer:
The value is 
Explanation:
Looking at the graph in the diagram we see each unit is equal to 1 both in the x axis and in the y- axis
Now the value of B along the x axis is

and along the y axis the value is

Hence the vector B is

The collapsed answer of Penchalreddy Badepalli is correct. The composition of two reflections via two mirror making an angle \alpha is equivalent to a single rotation by an angle 2\alpha, hence 2 * 60 deg = 120 deg. And turns is independent of the absolute orientation of the two mirrors in space and/or the direction of incidence of the incoming ray.
One could use elementary geometry to prove this (if you presume the direction of incidence is irrelevant imagine hitting the first mirror at 90 deg, then going retro right back along the normal to the first mirror, and follow the directions).
B they formed from the dense elements as compared to the others in the solar system
The pairs of triangles that can be proven congruent by the hl theorem is the right angled triangle.
<h3>What is mearnt be the HL theorm?</h3>
The HL theorem is also known as the Hypothenus Leg theorem, it states that "the hypotenuse and leg of one right triangle are congruent to the hypotenuse and leg of another right triangle, then the two triangles are congruent."
Learn more about the postulates of the HL theorem here:
brainly.com/question/25922842