Question

If sin x = .21,what is cos x?

Answer 1

sinx = 0.21

Using sin²x + cos²x = 1

0.21² + cos²x = 1

cos²x = 1 - 0.21² = 1 - 0.0441 =0.9559

cosx = √0.9559

cosx ≈ +0.978 or -0.978

Answer 2

Answer: The required value of cos x is 0.98 or -0.98.

Step-by-step explanation: We are given the value of the sine of an angle x as follows :

`\sin x=0.21`

We are to find the value of cos x.

We will be using the following trigonometric identity :

`\cos^2x+\sin^2x=1.`

We have

`\cos^2x=1-\sin^2x\\\\\Rightarrow \cos^2x=1-(0.21)^2\\\\ \Rightarrow \cos^2x=1-0.0441\\\\ \Rightarrow \cos x=\pm√(0.9559)\\\\ \Rightarrow \cos x=\pm 0.98.`

Thus, the required value of cos x is 0.98 or -0.98.