e) Trigonometry review: Double Angle Identities

Question 1

Double Angle Identity

sin 2a =

Answer 1

2 sin a cos a

Question 2

Double Angle Identity

• cos 2a =*
• ( 1^st version)*

Answer 2

cos² a - sin² a

Question 3

Double Angle Identity

cos 2a =

( 2^nd version )

Answer 3

2 cos² a - 1

Question 4

Double Angle Identity

cos 2a =

( 3^rd version )

Answer 4

1 - 2 sin² a

Question 5

Double Angle Identity

Answer 5