А15=а1+14d
–45,6+14d=2
14d=47,6
d=3,4
2a1+59d
S60 = ------------- • 60 = (2a1+59d)30=
2
=(2•(-45,6)+59•3,4)30=(–91,2+200,6)
•30 = 3282
Х= π/4-у ; tg(π/4-y -tgy ) 1/6; tgπ/4 -tgy -tgy =1/6; -2tgy= 1/6-1; -2tgy = -5/6; tgy= -5/6÷(-2)= 5/12; y = arctg5/12 + kπ;k∈Z; x= π/4 - arctg5/12+kπ; k∈Z.
0,25c^4-0,2c²d³+0,04d^6=(0,5c²-0,2d³)²