can you use latex to restate your problem?
The vector a depends on a parameter t, i.e. .. it satisfies the equation
show that , and .
For the vector a, find its value for t=pi if at t=0 and
i have absolutely no idea how to start...
Okay, go ahead and calculate . That's easy, it is just . Setting equal to that gives you three equations: , , and .
differentiating the first of those, with respect to t, gives . Get the point? I'll leave the others to you now.
For the last part you need to solve those equations. is easy: is a constant and the last part tells us that that constant is 1.
To solve the other two, use the fact, that you have now shown, that and . Solve those differential equations using the initial values , , , and .