- Thread starter
- #1
karush
Well-known member
- Jan 31, 2012
- 3,241
\(\displaystyle a=-4i-2j\) and \(\displaystyle b=i-7j\)
\(\displaystyle a\cdot b=(-4)(1)+(-2)(-7)=10\)
\(\displaystyle ||a||=\sqrt{(-4)^2+(-2)^2}=2\sqrt{5}\)
\(\displaystyle ||b||=\sqrt{1^2+(-7)^2}=5\sqrt{2} \)
\(\displaystyle \cos\theta = \frac{10}{10\sqrt{10}}\) so \(\displaystyle \theta\approx72^o\)
\(\displaystyle a\cdot b=(-4)(1)+(-2)(-7)=10\)
\(\displaystyle ||a||=\sqrt{(-4)^2+(-2)^2}=2\sqrt{5}\)
\(\displaystyle ||b||=\sqrt{1^2+(-7)^2}=5\sqrt{2} \)
\(\displaystyle \cos\theta = \frac{10}{10\sqrt{10}}\) so \(\displaystyle \theta\approx72^o\)
Last edited: