# Math Help - Prove that z^(k+1) is true for n=k+1

1. ## Prove that z^(k+1) is true for n=k+1

I'm having some problem recalling the trig identity.

I've work up till this part:

r^k . r^1 [Cos(k.theta)Cos(theta)-Sin(K.theta)Sin(theta)+i(Cos(theta)Sin(K.theta)+Co s(K.theta)Sin(theta)]

I need to reduce the above to its relevant trig identity to yield: r^(K+1) [Cos(K+1)theta + iSin(K+1)theta]

Solved: Thread to be delete

2. ## Re: Prove that z^(k+1) is true for n=k+1

Hey Darrykwc
I believe you are trying to prove De Moivre's Theorem.
Find the proof here
De Moivre's formula - Wikipedia, the free encyclopedia

3. ## Re: Prove that z^(k+1) is true for n=k+1

Originally Posted by Darrylcwc
I'm having some problem recalling the trig identity.

I've work up till this part:

r^k . r^1 [Cos(k.theta)Cos(theta)-Sin(K.theta)Sin(theta)+i(Cos(theta)Sin(K.theta)+Co s(K.theta)Sin(theta)]

I need to reduce the above to its relevant trig identity to yield: r^(K+1) [Cos(K+1)theta + iSin(K+1)theta]

Solved: Thread to be delete
No, the thread should NOT be deleted. Instead you should post your solution so that others who might be having a similar trouble in future might be able to refer to it.