Question

Cos87°•cos33°-sin87°•sin33°

Answer 1

Cos(87+33)=cos100=sin10

Answer 2

To calculate the value of the expression cos(87°)•cos(33°) - sin(87°)•sin(33°), you can use the trigonometric identity for the difference of angles:

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

In this case, A = 87° and B = 33°. So, the expression becomes:

cos(87° - 33°) = cos(54°)

Now, you can use the trigonometric identity for the complementary angle:

cos(90° - θ) = sin(θ)

Since 54° is the complementary angle to 36° (90° - 54° = 36°), we have:

cos(54°) = sin(36°)

So, the value of the expression is sin(36°). To find the numerical value, you can use a calculator or reference table. The value of sin(36°) is approximately 0.5878.