58°
72°
74°
87°
Correct answer is B
a.b=|a||b|cosθ
(131).(14)=13×1+1×4=13+4=17
17=(√132+12)(√12+42)cosθ
17=(√170)(√17)cosθ
cosθ=1717√10=√1010=0.3162
\theta = \cos^{-1} 0.3162 = 72°
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