Question

Найдите 2cos 2a, если sin a= -0,7​

Answer 1

Ответ:

Вот, держи, думаю понятно

Answer 2

To find the value of 2cos 2a when sin a = -0.7, we can use the Pythagorean identity:

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

Since sin a = -0.7, we can substitute it into the equation:

(-0.7)^2 + cos^2(a) = 1 0.49 + cos^2(a) = 1 cos^2(a) = 1 - 0.49 cos^2(a) = 0.51

Taking the square root of both sides, we get:

cos(a) = ±√(0.51)

Now, we can use the double-angle formula for cosine:

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

Substituting the value of cos^2(a), we have:

2(0.51) - 1 = cos(2a) 1.02 - 1 = cos(2a) 0.02 = cos(2a)

Therefore, 2cos 2a is equal to 0.02 when sin a = -0.7.