How can i find the angle between two vectors, given in the format '' i+j ''

You use the formula below ...,

Angle theta = cos^-1 [scalar product of the two vectors : multiplication of their moduli]

For example ... the angle between

(2i + 3j) and (4i + 5j)

Angle theta = cos^-1 [ (2 (4) + 3 (5)) : ((square root of (2^2 + 3^2)) * (square root of (4^2 + 5^2))

Angle theta = cos^-1 [ 23 : ((square root of (13)) * (square root of (41) ]

Angle theta = 5°