S=0,5sin B * AB * BC= 0,5 * 9 *16* 7/12= 42
1)12:4=3(м) легковых
2)12+3=15(М) вместе легковых и грузовых
3)15:5=3(м) мотоциклов
Ответ:3 мотоцикла было на стоянке.
1. 3 7/9 + 5 1/6 = (3 + 5) + (7/9 + 1/6) = 8 + (14/18 + 3/18) = 8 17/18,
2. 8 7/16 + 3 3/10 = (8 + 3) + (7/16 + 3/10) = 11 + (35/80 + 24/80) = 11 79/80,
3. 6 8/12 + 9 7/18 = (6 + 9) + (8/12 + 7/18) = 15 + (24/36 + 14/36) = 15 + 38/36 = 15 + 1 2/36 = 16 1/18,
4. 9 3/6 + 4 7/12 + 3 5/24 = (9 + 4 + 3) + (3/6 + 7/12 + 5/24) = 16 + (12/24 + 14/24 + 5/24) = 16 + 31/24 = 13 + 1 7/24 = 14 7/24.
sinx·siny=1/2( cos(x-y) -cos(x+y))
sinπ/5·sinπ/8=1/2(cos(π/5-π/8)- cos(π/5 +π/8)) = 1/2(cos3π/40 - cos13π/40)