Question

se cos 25* = 0,9 registre o valor aproximado de :

Answer 1

$\mathrm{\Rightarrow \cos{25\º}\approx0,9\approx\dfrac{9}{10}}$

$\mathrm{\mathbf{a)}\ \cos{155\º}=\cos{(180\º-25\º)}=}\\\\ \mathrm{=-\cos{25\º}+\approx-\dfrac{9}{10}\ \to\ \boxed{\mathbf{\cos{155\º}\approx-\dfrac{9}{10}}}}\\\\\\ \mathrm{\mathbf{b)}\ \cos{205\º}=\cos{(180\º+25\º)}=}\\\\ \mathrm{=-\cos{25\º}\approx-\dfrac{9}{10}\ \to\ \boxed{\mathbf{\cos{205\º}\approx-\dfrac{9}{10}}}}\\\\\\ \mathrm{\mathbf{c)}\ \cos{335\º}=\cos{(360\º-25\º)}=}\\\\ \mathrm{=\cos{25\º}\approx\dfrac{9}{10}\ \to\ \boxed{\mathbf{\cos{335\º}\approx\dfrac{9}{10}}}}$