Question

Aratati ca 1/(sin60°- sin30°)(cos60°+cos30°) apartine lui N

Answer 1

1/[(sin60°-sin30°)(cos60°+cos30°)]=$\frac{1}{( \frac{ \sqrt{3} }{2}- \frac{1}{2})( \frac{1}{2}+ \frac{ \sqrt{3} }{2}) }=$$\frac{1}{ \frac{3}{4}- \frac{1}{4} } = \frac{1}{ \frac{2}{4} }=2$ ∈ N