Odpowiedzi

2010-01-04T13:38:49+01:00
Sinα * cosα = 1/2 * (2 * sinα * cosα) = 1/2 * (1 + 2 * sinα * cosα - 1) =
= 1/2 * (sin²α + cos²α + 2 * sinα * cosα - 1) =
= 1/2 * ((sinα + cosα)² - 1) =
= 1/2 * ((2√3/3)² - 1) =
= 1/2 * (4 * 3 / 9 - 1) = 1/2 * (4/3 - 1) = 1/2 * 1/3 = 1/6