SOLUTION: 1) use Euler's formula to determine the standard trigonometric identity for cos(alpha+beta).

SOLUTION: 1) use Euler's formula to determine the standard trigonometric identity for cos(alpha+beta).

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Question 114238: 1) use Euler's formula to determine the standard trigonometric identity for cos(alpha+beta).
Answer by solver91311(24713) (Show Source): You can put this solution on YOUR website!
Euler's Formula is:

Apply this formula to

But

So

Which is to say,

Expanding the right side using FOIL yields:

And gathering like terms:

Since we know that if and only if and ,
we can see that:

, which is the desired identity.

By the way, we have also proven the companion identity:

Hope this helps,
John

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