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3-1.Vectors
medium
सदिशों $(\hat i + \hat j)$ तथा $(\hat j + \hat k)$ के बीच कोण ....... $^o$ है
A
$30$
B
$45$
C
$60$
D
$90$
Solution
(c) $(\hat i + \hat j).(\hat j + \hat k) = 0 + 0 + 1 + 0 = 1$
$\cos \theta = \frac{{\mathop A\limits^ \to .\mathop B\limits^ \to }}{{|\mathop A\limits^ \to ||\overrightarrow {\,B} |}} = \frac{1}{{\sqrt 2 \times \sqrt 2 }} = \frac{1}{2}$
$\theta = 60^\circ $
Standard 11
Physics
