Question

ex : 13 și 14
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Answer 1

Răspuns:

Explicatie pas cu pas:

Answer 2

13.

$\it \ cos20^o=sin(90^o-20^o)=sin70^o>sin50^o$

14.

$\it \left.\begin{aligned} \it sin3-sin1=2sin\dfrac{3-1}{2}cos\dfrac{3+1}{2}=2sin1cos2 \\ \\ \\ \it 2\in \Big(\dfrac{\pi}{2},\ \pi\Big) \Rightarrow cos2<0\ \ \ \ \ \ \ \ \ \end{aligned}\right\} \Rightarrow 2sin1cos2<0\Rightarrow\\ \\ \\ sin3-sin1<0 \Rightarrow sin3<sin1$