Question

Cos2f cos3f +sin2f sin3f​

Answer 1

Ответ:

cos2f•cos3f+sin2f+sin3f=-18•-18+-17•-17=-613

Answer 2

Ответ:

Объяснение:

=сos(2f-3f)=cos(-f)=cosf,   (это по формуле  cos(a-b)=cosa*cosb+sina*sinb)

Answer 3

The expression you've provided seems to be a trigonometric expression involving the cosine and sine functions with angles 2f and 3f. You can simplify this expression using trigonometric identities.

Let's start by using the product-to-sum identities for cosine and sine:

1. Cos(A)Cos(B) = (1/2)[Cos(A + B) + Cos(A - B)]
2. Sin(A)Sin(B) = (1/2)[Cos(A - B) - Cos(A + B)]

Now, let's apply these identities to your expression:

Cos(2f)Cos(3f) + Sin(2f)Sin(3f)

= (1/2)[Cos(2f + 3f) + Cos(2f - 3f)] + (1/2)[Cos(2f - 3f) - Cos(2f + 3f)]

Notice that the terms with Cos(2f - 3f) cancel out when you add the two halves together:

= (1/2)[Cos(5f) + Cos(-5f)]

Now, Cos(-x) = Cos(x), so the expression simplifies further:

= (1/2)[Cos(5f) + Cos(5f)]

= (1/2)(2Cos(5f))

= Cos(5f)

So, the simplified expression is Cos(5f).