Question

Find a · b. |a| = 60, |b| = 90, the angle between a and b is 3π/4.

Answer 1

By definition, the dot product between two vectors is given by:

$a.b = | a || b | cos (\alpha)$

We have then that for this case:

$| a | = 60$

$| b | = 90$

$\alpha = \frac{3\pi}{4}$

Therefore, substituting values we have:

$a.b = | 60 || 90 | cos (\frac{3\pi}{4})$

$a.b = -3818$

Answer:

The product point of the vectors is:

$a.b = -3818$