Question

Вычислить cos(3pi/2 +a), если cosa=-0.8 и pi < a <3pi/2

Answer 1

I hope this helps you

Answer 2

To calculate cos(3π/2 + a) given that cos(a) = -0.8 and π < a < 3π/2, we can use trigonometric identities.

Since π < a < 3π/2, we know that a is in the third quadrant. In the third quadrant, the cosine function is negative.

We can use the identity cos(θ) = cos(-θ) to rewrite the expression as follows:

cos(3π/2 + a) = cos(-(3π/2 - a))

Now, let's find the value of (3π/2 - a):

(3π/2 - a) = (3π/2) - a

Now, we know that cos(θ) = -0.8. Let's find the value of cos((3π/2 - a)) using this information:

cos((3π/2 - a)) = cos(θ) = -0.8

Since the cosine function is negative in the third quadrant, the negative sign will remain:

cos(-(3π/2 - a)) = -(-0.8) = 0.8

So, the value of cos(3π/2 + a) is 0.8.