А)( а – 3 )^2 =а²-6а+9<span>
б)( 2х + у )^2 =4х</span>²+4ху+у²<span>
в)( 5в – 4х )( 5в + 4х )=25в</span>²-16х²
а) 4а( а – 2 ) – ( а – 4 )^2 =4а²-8а-а²+8а+16=3а²+16<span>
б) 2( в + 1 )^2 – 4в =2в</span>²+4в+2-4в=2в²+2
<span>а) х^2 – 25 =(х-5)(х+5)
б) ав^ 2 – ас^ 2 =а(в-с)(в+с)
</span>в). – 3а^ 2 – 6ав – 3в^ 2=-3(а²+2ав+в²)=-3(а+в)²
<span>а). 25а ^2 – ( а + 3 )^ 2=25а</span>²-а²-6а-9=24а²-6а-9<span>
в). 16х ^4 – 81 =(4х</span>²-9)(4х²+9)<span>
</span>
cost = 3/4
cos(t/2) = ((1 + cost)/2)^(1/2) = ((1 + 3/4)/2)^(1/2) = (7/8)^(1/2) = (7^(1/2))/(2*(2^(1/2)))
sin(t/2) = (1 - cos^2(t/2))^(1/2) = (1 - 7/8)^(1/2) = 1/(8^(1/2)) = 1/(2*(2^(1/2)))
tg(t/2) = sin(t/2)/cos(t/2) = (1/(2*(2^(1/2))))/((7^(1/2))/(2*(2^(1/2)))) = 1/(7^(1/2))
ctg(t/2) = 1/tg(t/2) = 7^(1/2)
15%=0,15
0,15 * 620=93 (га) - убрали за сутки
Ответ: 93 га