Question

Vector A has magnitude 5 units and is in the direction of +x axis​

Answer 1

Answer

Angle between the vectors = 90 degrees

The magnitude of their crossproduct = 5x9 sin90 = 45 units

Its direction is along the perpendicularly the plane containing z axis(vectorB) and vectorA

Explanation

x, y and z axis are mutually perpendicular. Which also leads to the conclusion that z-axis is perpendicular to x-y plane.

Now, according to given problem, vector-A lies in x-y plane and vector-B lies along z-axis. Hence, it can be said that vector-A and vector-B are perpendicular i.e. the angle between them is 90° .

A×B= A*B* sin( 90°)

A×B= 5*9*1

A×B= 45.

Answer 2

Therefore,

A= 5i

When a vector is in x direction we use i for indicating its x direction