21) tan=sin/cos = 1/2.5=0.4
3cos/cos+ 8sin/cos=3+8tan
22) (2a-b)^2=0.64
2a-b=0.8
3^10a
= 3^(10a-5b)
3^5b
23) (9+10.8)/3.6=0.55
средняя скорость =4.95км/ч
