Select the best answer.cos20°cos30° - sin20°sin30° = cos

The equation you provided is a form of the cosine of the sum of two angles identity, which is:

cos(a + b) = cos(a)cos(b) - sin(a)sin(b)

So, cos20°cos30° - sin20°sin30° equals to cos(20° + 30°) = cos50°.

The answer to your question is based on the formula for the cosine of the sum of two angles. The formula is:

cos(a + b) = cos(a)cos(b) - sin(a)sin(b)

So, cos20°cos30° - sin20°sin30° is equivalent to cos(20° + 30°) = cos50°. Therefore, the answer is cos50°.