cos50°/sin25°+cos25°. Created by enderman3025. algebra-ru

sin25°+cos25°...

veroniuka11

Ответ:

$\dfrac{cos50^\circ }{sin25^\circ +cos25^\circ }=\dfrac{cos^225^\circ -sin^225^\citc }{sin25^\circ +cos25^\circ }=\dfrac{(sin25^\circ -cos25^\circ )(sin25^\circ +cos25^\circ )}{sin25^\circ +cos25^\circ }=\\\\\\=sin25^\circ -cos25^\circ =sin25^\circ -cos(90^\circ -65^\circ )=sin25^\circ -sin65^\circ =\\\\\\=2\, sin\dfrac{25^\circ -65^\circ }{2}\cdot cos\dfrac{25^\circ +65^\circ }{2}=-2\, sin20^\circ \cdot cos45^\circ =-\sqrt2\, sin20^\circ$

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NNNLLL54

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Отв: ~2,42727

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uprostit 1cos2atga sin2a

2a 2sinacosp a

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