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 :
[tex]\sin x=0.21[/tex]
We are to find the value of cos x.
We will be using the following trigonometric identity :
[tex]\cos^2x+\sin^2x=1.[/tex]
We have
[tex]\cos^2x=1-\sin^2x\\\\\Rightarrow \cos^2x=1-(0.21)^2\\\\ \Rightarrow \cos^2x=1-0.0441\\\\ \Rightarrow \cos x=\pm\sqrt{0.9559}\\\\ \Rightarrow \cos x=\pm 0.98.[/tex]
Thus, the required value of cos x is 0.98 or -0.98.
