1.

Evaluate:(sin 72° + cos 18°) (sin 72° – cos 18°)

Answer»

We know that, 

sin (90 – θ) = cos θ 

So, the given can be expressed as 

(sin 72° + cos 18°) (sin (90 – 18)° – cos 18°) 

= (sin 72° + cos 18°) (cos 18° – cos 18°) 

= (sin 72° + cos 18°) x 0 

= 0



Discussion

No Comment Found