Question

cos 2a-sinA seca -cosa
​

Answer 1

Answer:

sin

2

A+cos

2

A=1. Its a standard identity.

We know that sinA=

H

P

and cosA=

H

B

Hence sin

2

A=

H

2

P

2

and cos

2

A=

H

2

B

2

Hence adding the above given functions sin

2

A+cos

2

A we get

sin

2

A+cos

2

A=

H

2

H

2

=1

Using P

2

+B

2

=H

2

by Pythagoras Theorem