Question

verify that cos 60degree=cos^2 30degree =sin^2 30degree=1/2

Answer 1

cos60°=

2

1

⇒1−2sin

2

30°=1−2(

2

1

)

2

=1−

2

1

=

2

1

⇒2cos

2

30°−1=2(

2

3

)

2

=

2

3

−1=

2

1

∴cos60°=1−2sin

2

30°=2cos

2

30°−1

Hence, the answer is verify.