2x-π/2=π/6+πn
2x=π/6+π/2+πn
2x=4π/6+πn
2x=2π/3+πn
x=π/3+πn/2
4) 2sin (π+3/4x-3π/2+3/4 x) /2 *cos ( π+3/4x+3π/2-3/4x)/2 =0
2sin( -π/2+6/4x) /2 * cos(5π/2)=0
sin(-π/2+6/4x)=0
-π/2+6/4x=πn
6/4x=π/2+πn
x=π/2*4/6 + 4πn/6
x=π/3+ 2πn/3
4м/с=240м/мин=14400м/ч=14,4км/ч
10м/с=600м/мин=36000м/ч=36км/ч
<span> (x+5,7):5,1=2
х+5,7=2*5,1
х+5,7=10,2
х=10,2-5,7
х=4,5</span>