Math Help

Archive for August, 2008

Integration Problem: 

Evaluate 

 

where 

u = x 

dv = cos x dx 

du = dx 

v = sin x 

---

Answer: 

 

= x sin x – ( – cos x ) + c 

= x sin x + cos x + c

Question: Math Help needed with imaginary numbers?

Imaginary numbers; conjugate pairs

-sqrt(6) + 3i
_____________
sqrt(5) – 3i
I get the conjugate part it is ‘cleaning up’ the numerator that gets me
Thanks for the help i got stuck up to isolation of the ‘a’ answer and ‘bi’ answer. completely forgot to pull out the i. Thanks for your help all

Answer: ( -√6 + 3i ) / ( √5 – 3i )
= [ (-√6 + 3i)(√5 + 3i) ] / [ (√5 - 3i)(√5 + 3i) ]
= ( -√6√5 – 3i√6 + 3i√5 + 9i^2 ) / ( 5 – 9i^2 )
= [ -√30 + (3√5 - 3√6)i + 9(-1) ] / [ 5 - 9(-1) ]
= [ (-√30 - 9) + (3√5 - 3√6)i ] / 14

It is messy but just FOIL it!

I hope that helps!

Imaginary Numbers – YourTeacher.com – Algebra 2 Help