Question 224325
Do you mean the interval t=30 to t=40? That's what it appears to be.
The term
{{{6cos(30/3))}}} should be negative.
The 25's in the NUM cancel.
--> 0.6(cos(40/3) - cos(10))
= 0.6*-0.11762...
= ~ - 0.0070577...