Question

what is the formula of cos 2a​

Answer 1

Answer:

The formula cos 2A = cos2 A − sin2 A

We now examine this formula more closely.

We know from an important trigonometric identity that

cos2 A + sin2 A = 1

so that by rearrangement

sin2 A = 1 − cos2 A.

So using this result we can replace the term sin2 A in the double angle formula. This gives

cos 2A = cos2 A − sin2 A

= cos2 A − (1 − cos2 A)

= 2 cos2 A − 1

Answer 2

Answer:

cos2a = cos²a - sin²a

#Secretgirl✌️