Question

Найдите значение выражения cos2x, если cosx=-0,6.

Answer 1

cos2x=cos^2x-sin^2x

sin^2x=1-0.36

sin^2x=0.64

cos2x=(-0.6)^2-0.64=-0.28

Answer 2

1-2sin^2 x = 3/5;
sin^2 x = 1/5
sin x = 1/sqrt(5)
cos x = 2/sqrt(5);
tg x = 0,5
ctg x = 2;

Answer 3

I can help you with your math question.

To find the value of $\cos 2x$, we can use the double angle formula: $\cos 2x = 2\cos^2 x - 1$. If $\cos x = -0.6$, then $\cos^2 x = 0.36$. Plugging this into the formula, we get:

$$\cos 2x = 2(0.36) - 1$$ $$\cos 2x = -0.28$$

Therefore, the value of $\cos 2x$ is $-0.28$ when $\cos x = -0.6$.

You can also use the web search results to learn more about this topic. For example, you can see the graph of $y = \cos 2x$ [here](https://www.mathway.com/ru/popular-problems/Algebra/238351) or read about how to solve trigonometric equations [here](https://www.kontrolnaya-rabota.ru/s/equal-one/any-uravnenie/e/kosinus_ot_2_x_plyus_kosinus_ot_x_ravno_nol/).