Question

1. Find the value of cos 2x when
9
() sin x = =
10​

Answer 1

Answer:

what is your question?

what should we find?

Answer 2

Answer:

Answer:

cos 2x = -0.62

Step-by-step explanation:

We have sin x = 9/10 = 0.9

Therefore,

{ \sin }^{2} (x) = 0.81sin

2

(x)=0.81

Using,

\begin{gathered} {sin}^{2} (x) + {cos}^{2} (x) = 1 \\ {cos}^{2} (x) = \frac{19}{100} \end{gathered}

sin

2

(x)+cos

2

(x)=1

cos

2

(x)=

100

19

We know,

\begin{gathered} \cos(2x) = {cos}^{2} (x) - {sin}^{2} (x) \\ \cos(2x) = \frac{19}{100} - \frac{81}{100} \\ \cos(2x) = - 0.62\end{gathered}

cos(2x)=cos

2

(x)−sin

2

(x)

cos(2x)=

100

19

−

100

81

cos(2x)=−0.62