If sin C =9/10, then what is the value of cos2 C ?

We are given that ,

sin C = \(\frac{9}{10}\)

Now,

cos² C

{ using , sin²x + cos²x = 1 }

= ( 1 - sin²C )

= 1 - \(\frac{81}{100}\)

= \(\frac{19}{100}\)