Answer:
Step-by-step explanation:
Cos θ = u*v
IuI *IvI
u * v = 7*(-1) + (-2)*2
= -7 - 4
= -11
IuI = [tex]\sqrt{7^{2}+(-2)^{2}}\\[/tex]
= [tex]\sqrt{49+4}\\\\[/tex]
= [tex]\sqrt{53}[/tex]
I vI = [tex]\sqrt{(-1)^{2}+2^{2}}\\[/tex]
= [tex]\sqrt{1+4}\\\\[/tex]
= [tex]\sqrt{5}\\[/tex]
Cos θ = [tex]\frac{-11}{\sqrt{53}*\sqrt{5} } \\\\[/tex]
= [tex]\frac{-11}{16.28}\\\\[/tex]
Cos θ = -0.68
θ = 132.5°
