Question

Cos2a cosa-sin2a sina

Answer 1

Здесь используется формула косинуса суммы углов.


cos2acosa-sin2asina=cos(2a+a)= cos3 a

Answer 2

It appears that you want to expand the expression "cos(2a) cos(a) - sin(2a) sin(a)." You can simplify this expression using trigonometric identities.

Using the double angle identity for cosine and the identity for sine, you can simplify as follows:

cos(2a) = 2cos^2(a) - 1 sin(2a) = 2sin(a)cos(a)

Now, substitute these identities into your expression:

2cos^2(a) - 1 * cos(a) - 2sin(a)cos(a) * sin(a)

Now, distribute the terms:

2cos^3(a) - cos(a) - 2sin^2(a)cos^2(a)

You can simplify this further if needed, but this is the expanded expression for "cos(2a) cos(a) - sin(2a) sin(a)."