MATLAB: Simplifying solution of a differential equation

differentialequationoutputsimplification

The most simplified version of ySol(t), the solution to the differential equation below, is 1.5*sin(2t+0.7297), but the output of the following code is in terms of exponential functions. Can someone explain how the output can be further simplified? 
syms y(t) m k 
Dy = diff(y,t); Dy2 = diff(y,t,2);  
ode = m*Dy2 + k*y == 0;
cond = [y(0) == 1,Dy(0) == sqrt(5)];
ySol(t) = dsolve(ode,cond)
ySol(t) = simplify(ySol(t),'steps',500)
pretty(ySol(t))

Best Answer

m = rand(); k = rand();
syms y(t)
Dy = diff(y,t);
Dy2 = diff(y,t,2);  
ode = m*Dy2 + k*y == 0;
cond = [y(0) == 1,Dy(0) == sqrt(5)];
ySol(t) = dsolve(ode,cond)
ySol(t) = 
ySol(t) = simplify(ySol(t),'steps',500)
ySol(t) = 
pretty(ySol(t))
                                                                                     / sqrt(43198488722811199054095930230) t \
                                               sqrt(8639697744562239810819186046) sin| ------------------------------------- | 5
   / sqrt(43198488722811199054095930230) t \                                         \            157178273090335            /
cos| ------------------------------------- | + ---------------------------------------------------------------------------------
   \            157178273090335            /                                    274837532398538
vpa(ySol(t), 5)
ans = 
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