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causingaruckus,eh? 2 years ago Find the norm of vector r prime of t when r(t) = t^2i + 2sintj + 2costk

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1. modphysnoob

r'(t)=? r(t) is given

2. modphysnoob

so start with taking derivative

3. modphysnoob

then square each component , add them

4. modphysnoob

take square root

5. causingaruckus,eh?

$\sqrt(4t^2 + 4\cos^2t + 4\sin^2t)$

6. causingaruckus,eh?

What's the trig identity for cos and sin?

7. modphysnoob

cos^2 t + sin^2 t =1

8. causingaruckus,eh?

so does the second half of that just become 8?

9. modphysnoob

4( 1)=4

10. causingaruckus,eh?

Can you explain? I can never follow this one...

11. modphysnoob

cos(t)^2+sin(t)^2=1 4(cos(t)^2+sin(t)^2)=4

12. causingaruckus,eh?

Ohhhh.... Is that technically combining like terms?

13. modphysnoob

I guess

14. causingaruckus,eh?

Thanks!

15. modphysnoob

no problem

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