Question

найдите 4cos2a, если sina= -0.5

Answer 1

кос 2 а = 1 - 2 син в квадрате а

кос 2 а = 1 - (-0.5) в квадрате = 1 - 0,25 = 0,75

4 кос 2 а = 0,75 * 4 = 3

 

Answer 2

To find the value of 4cos(2a) given that sin(a) = -0.5, we can use the trigonometric identity:

cos(2a) = 1 - 2sin^2(a)

Let's substitute the given value of sin(a) into the identity:

cos(2a) = 1 - 2(-0.5)^2

Simplifying the expression:

cos(2a) = 1 - 2(0.25)

cos(2a) = 1 - 0.5

cos(2a) = 0.5

Now, we need to find 4cos(2a):

4cos(2a) = 4 * 0.5

4cos(2a) = 2

Therefore, when sin(a) = -0.5, the value of 4cos(2a) is 2.