Find λ if the Vectors A and B are perpendicular | Dot Product

What is dot product (scalar product)?

The dot product, also called scalar product, is a measure of how closely two vectors align, in terms of the directions they point. The measure is a scalar number (single value) that can be used to compare the two vectors and to understand the impact of repositioning one or both of them. The dot product is obtained by performing mathematical calculations on the vector properties.
A vector is a quantity that has both direction and magnitude (the vector's length). Figure 1 shows two vectors (a and b) on a two-dimensional Cartesian plane. Vector a has a magnitude of 8 and is at a 115-degree angle from the x-axis (moving counterclockwise). Vector b has a magnitude of 10 and is at a 45-degree angle from the x-axis. The angle between the two vectors -- represented by the Greek letter theta (θ) -- is 70 degrees, which is calculated by subtracting 45 degrees from 115 degrees.