Question

Cos3x cosx - sin3x sinx ​

Answer 1

решение задания смотри на фотографии

Answer 2

To simplify the expression cos(3x)cos(x) - sin(3x)sin(x), we can use the trigonometric identity for the cosine of the difference of angles:

cos(A - B) = cos(A)cos(B) + sin(A)sin(B)

In this case, let's rewrite the expression using the identity:

cos(3x)cos(x) - sin(3x)sin(x) = cos(3x - x)

Simplifying the angle inside the cosine function:

cos(3x - x) = cos(2x)

Therefore, the simplified expression is cos(2x).