Answer:
Cos(a - b) = 0.959
Step-by-step explanation:
We know that:
Sin(a) = 4/5
Such that a is on the first quadrant (between 0° and 90°)
then:
Sin(a) = 4/5
Asin(sin(a)) = Asin(4/5)
a = Asin(4/5) = 53.13°
And:
Cos(b) = 2/5
Then:
Acos(Cos(b)) = Acos(2/5)
b = Acos(2/5) = 36.67°
Then:
Cos(a - b)
where:
a = 53.13° and b = 36.67°
Then:
Cos(a - b) = Cos(53.13° - 36.67°) = 0.959
