a) π/2<t<π - 2-ая четверть
cost - " - "
tgt и ctgt - " - "
cost = -√(1-(4/5)²) = - √(1 - 16/25) = - √9/25 = -3/5
tgt = sint / cost = 4/5 : (-3/5) = -4/3
ctgt = 1/tgt = -3/4
б) 0<t<π/2 - 1-ая четверть
cost , tgt, ctgt - " + "
cost = √(1-(5/13)²) = √(1- 25/169) = √(144/169) = 12/13
tgt= 5/13 : (12/13)=5/12
ctgt = 12/5
в) -π/2<t<0 - 4-ая четверть
cost - " + "
tgt, ctgt - " - "
cost = √(1-(-0.6)²) = √(1-0.36) = √0.64 = 0.8
tgt = -0.6 / 0.8 = - 6/8 = - 3/4
ctgt = - 4/3
г) π<t<3π/2 - 3-я четверть
cost - " - "
tgt, ctgt - " + "
cost = - √(1-(-0.28)²) = - √0.9216 = - 0.96
tgt = -0.28 / (-0.96) = 28/96 = 7/24
ctgt = 24/7 = 3 ³/₇
Пошаговое объяснение:
1) (5 целых 1/6 - 3,25) × 4/23
5 1/6-3.25=31/6-13/4=62/12-39/12=23/12
23/12*4/23=1/3
2) (21,3 - 18 целых 3/4) × 3,4
21.3-18 3/4=21.3-18.75=2.55
2.55*3.4=8.67
3) 2 целых 1/7 : 5/6 × 7/9 - 1,9
2 1/7:5/6=15/7*6/5=18/7
18/7*7/9=2
2-1.9=0,1