Răspunsuri

2014-05-05T18:04:53+03:00
Conform formulei 
sin(a)cos(b) = \frac{sin(a+b)+sin(a-b)}{2}
rezulta ca
sin(b)cos(b) =  \frac{sin(2b)+sin(0)}{2} =  \frac{sin(2b)}{2}
orice sin este ≤ 1 ⇒ sin(b)cos(b) =  \frac{sin(2b)}{2}  ≤  \frac{1}{2}
or, cum sin(30) =   \frac{1}{2}  ⇒ sin(b) x cos(b) ≤ sin(30)