a⋅b=∣a∣∣b∣cosθa \cdot b = |a||b|\cos \thetaa⋅b=∣a∣∣b∣cosθ
cosθ=a⋅b∣a∣∣b∣\cos \theta = \frac{a \cdot b}{|a||b|}cosθ=∣a∣∣b∣a⋅b
= (5i+3j)⋅(3i−5j)(52+32)(32+(−5)2)\frac{(5i+3j)\cdot(3i-5j)}{(\sqrt{5^2+3^2})(\sqrt{3^2+(-5)^2})}(52+32)(32+(−5)2)(5i+3j)⋅(3i−5j)
= 034=0\frac{0}{34} = 0340=0
θ=cos−10=90∘\theta = \cos^{-1} 0 = 90^{\circ}θ=cos−10=90∘
