Question

решите пожалуйста..
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Answer 1

1) Неверно утверждение "в" ,  так как по теореме косинусов :

$\displaystyle\bf\\a^{2}=b^{2} +c^{2} -2bcCos\alpha$

$\displaystyle\bf\\2)\\\\\frac{NK}{Sin < M} =2R\\\\\\\frac{2\sqrt{2} }{Sin45^\circ } =D\\\\\\D=\frac{2\sqrt{2} }{\frac{1}{\sqrt{2} } } =2\sqrt{2} \cdot\sqrt{2}=4\\\\\\D=4\\\\3)\\\\\frac{\sqrt{12} }{Sin\beta } =2\cdot 2\\\\\\\frac{2\sqrt{3} }{Sin\beta } =4\\\\\\Sin\beta =\frac{2\sqrt{3} }{4} =\frac{\sqrt{3} }{2} \\\\\\\beta =60^\circ\\\\4)\\\\AB^{2} =BC^{2} +AC^{2}-2\cdot BC\cdot AC\cdot Cos120^\circ\\\\AB^{2} =9+25-2\cdot 3\cdot 5\cdot\Big(-\frac{1}{2} \Big)$

$\displaystyle\bf\\AB^{2} =34+15=49\\\\AB=\sqrt{49} =7\\\\AB=7$