Answer:
cos(60) cos(-20) - sin(60) sin(-20) = cos (40)
Step-by-step explanation:
Using the trigonometric identity rule:
[tex]\cos(A+B) = \cos A \cos B- \sin A \sin B[/tex]
Given that:
cos(60) cos(-20) - sin(60) sin(-20)
Let A = 60 and B = -20
then;
Using identity rule:
[tex]\cos (60) \cos (-20)- \sin (60) \sin (-20) = \cos(60+(-20)) = \cos (60-20)=\cos 40[/tex]
Therefore, the following as a function of a single angle is cos (40)
