Question

Prove that cos 5° - sin25º = sin35°

Answer 1

Answer:

L.H.S = cos5 – sin 25

= sin 95 – sin 25 [ sin(90+5) = cos5 ]

= 2 * cos (95+25)/2 * sin (95-25)/2

= 2 * cos60 * sin35

=2 * ½ * sin35 (cos60 = ½ )

= sin35

= R.H.S

hence L.H.S = R.H.S

Answer 2

Question

Prove that cos 5° - sin25º = sin35°

Solutiom

L.H.S = cos5 – sin 25

= sin 95 – sin 25 [ sin(90+5) = cos5 ]

= 2 * cos (95+25)/2 * sin (95-25)/2

= 2 * cos60 * sin35

=2 * ½ * sin35 (cos60 = ½ )

= sin35

= R.H.S

hence,L.H.S = R.H.S

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