Ariel is putting together lunch bags for 12 students going on a field trip. she put 5 apple slices and 6 orange slices into each bag. how many apple slices and orange slices does ariel need?

The answer is the second ⇒ cosx cosπ - sinx sinπ

Step-by-step explanation:

∵ cos(x + π) = cosx cosπ - sinx sinπ

∵ cosπ = -1

∵ sinπ = 0

∴ cos(x + π) = cosx(-1) - sinx(0) = -cosx - 0 = -cosx

The mistake in the rule it will not give different answer because + 0 or - 0 give us the same answer but if the measure of angle not π the answer will change.

Note: cos(x + π) means the angle in the third quadrant and the value of cos in the third quadrant must be negative