Question

Cos2a+cos3a..........​

Answer 1

Держи, делай всё точь-в-точь, но делай отметку по 1 клетке.

Answer 2

The expression you provided appears to be incomplete. It seems like you want to find the sum of the cosines of angles in a sequence, but the sequence itself is not specified.

Assuming you meant to provide a sequence of angles and you want to find the sum of their cosines, let's say the sequence of angles is a, 2a, 3a, and so on up to n terms. Then, the sum of their cosines can be calculated as follows:

Sum = cos(a) + cos(2a) + cos(3a) + ... + cos(na)

There is no simple general formula for this sum when you have an arbitrary number of terms (n) in the sequence. However, it is possible to express this sum using complex numbers and geometric series for specific values of n.

For instance, if n = 1, the sum is simply:

Sum (n = 1) = cos(a)

If n = 2, the sum is:

Sum (n = 2) = cos(a) + cos(2a)

If n = 3, the sum is:

Sum (n = 3) = cos(a) + cos(2a) + cos(3a)

And so on.

If you have a specific value for 'n' or a different sequence of angles in mind, please provide that information so that I can assist you with the exact calculation of the sum.