Question

find the exact value of sin a = 4/5, a lies in quadrant 2, and cos B = 2/5, B lies in quadrant 1 find cos(a-b)​

Answer 1

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