Question

Cos7xcos9x-sin7xsin9x

Answer 1

Ответ:

Решение представлено на фотографии

Answer 2

To simplify the expression cos(7x)cos(9x) - sin(7x)sin(9x), you can use the trigonometric identity for the cosine of the difference of two angles:

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

In your case, A = 7x and B = 9x. So, the expression becomes:

cos(7x - 9x)

Now, simplify the exponent:

cos(-2x)

Using the even symmetry property of the cosine function (cos(-x) = cos(x)), we can further simplify:

cos(2x)

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