Asystem of two differential equations with real-valued coefficients has the complex solution el1+)t(- 1 2 i 2 2 i then two real-valued solutions are given by -cos (t) and e\2 cos (t)) a) -2 sin (t) e -2 sin (t) 2 sin (t)- cos (t) ,) b) and 2 sin (t)+2 cos (t) e -sin (t)- 2 cos (t) 2 sin (t)- 2 cos (t)
-2 sin (t) - cos () | and 2 cos (t)-2 sin (t) c) e -sin (t) 2 cos (t) 2 sin (t)-2 cos (t) 2 i sin (i t)-cos (i t) and 2 i sin (i t)+2 cos (i t) d) -i sin (i t) - 2 cos (i t) 2 i sin (i t)-2 cos (i t).