## krypton 3 years ago i need help with number 3 a and b

1. krypton

2. krypton

pls help

3. ivanmlerner

The opposite of derivative is integration, so in a you need to integrate once and on b, twice. Since the indefinite integral (with no limits of integration) gives you an arbitrary constant that disapears when you derivate, you need a way to find that constant because any number would satisfy the derivative formula since it would disapear when you derivated, thats why they give you one value of the function you want to find. Is it too confusing the way I explained or you got it?

4. krypton

b was the confusing one,so am to integrate t-cosx 2twice?

5. ivanmlerner

Yes, because you are derivating twice, but then you get 2 arbitrary constants.

6. krypton

whats this for dy(0)/dx=2 what do i need it for?

7. krypton

my first integration i got tx-sin(x)+c

8. ivanmlerner

Your integration is fine and now you need to determine c, thats when you use dy(0)/dx=2, because by integrating once, you got dy/dx

9. krypton

so how do i use this dy(0)/dx=2?

10. ivanmlerner

tx-sin(x)+c=dy/dx so t*0-sin(0)+c=2 Do you understand that?

11. krypton

yeah

12. krypton

so what about the y(0)=-2?

13. ivanmlerner

you have dy/dx, but you want y, so you integrate again, and youll need this to find the other constant.

14. ivanmlerner

So, did you got the answer?

15. krypton

i will integrate this tx-sin(x)+c again?

16. ivanmlerner

yes

17. ivanmlerner

because it is equal to dy/dx, and you want y

18. krypton

i got (tx^2/2)+cos(x)+c

19. ivanmlerner

you forgot to sonsider the constant of the previous integration

20. ivanmlerner

There will be two constants in this case, because its the second derivative.

21. krypton

cx+tx^2/2+cos(x)+c?

22. ivanmlerner

Yep thats it, but keep in mind that the c's are different, and the first one you should already have it as a number

23. krypton

the 1st one is 2 right?

24. ivanmlerner

yes

25. krypton

ok thanks alot for your help :)

26. ivanmlerner

You are welcome