Question

Cos80°cos20°+sin80°sin20°​

Answer 1

Ответ:

1/2

Объяснение:

cosa×cosb+sina×sinb=cos(a-b)

cos(a-b)=cos(80°-20°)

=60°=1/2

Answer 2

The expression you've given is an example of the trigonometric identity for the cosine of the difference of two angles, which is commonly known as the cosine of the angle difference formula:

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

In your expression, A is 80 degrees, and B is 20 degrees. So, applying the formula:

cos(80° - 20°) = cos(60°)

Now, the cosine of 60 degrees is a well-known value:

cos(60°) = 1/2

So, your expression simplifies to:

1/2