Question

prove that: sec 70 sin 20 = cosec 70 cos 20​

Answer 1

Answer:

Step-by-step explanation:

L.H.S. = sec 70 sin 20

= sec ( 90 - 20 ) sin 20

= cosec 20 sin 20 ( ∵ sec ( 90 - x ) = cosec x )

= ( 1 / sin 20 ) sin 20 ( ∵ cosec x = 1 / sin x )

= 1

R.H.S. = cosec 70 cos 20

= cosec ( 90 - 20 ) cos 20

= sec 20 cos 20 ( ∵ cosec ( 90 - x ) = sec x )

= ( 1 / cos 20 ) cos 20 ( ∵ sec x = 1 / cos x )

= 1

∴ L.H.S. = R.H.S. is proved