Question

3cos51/sin39-2sin15/cos75

Answer 1

We have,
3cos51/sin39-2sin15/cos75
= 3cos(90-39)/sin39-2sin(90-75)/cos75
= 3sin39/sin39-2cos75/75 ( because cos (90-a)= Sin a )
Now, 3-2=1, ans

Answer 2

3(cos51°)/(sin39°) - 2(sin15°)/(cos75°)
=3[cos(90°-39°)]/(sin39°) - 2[sin(90°-75°)]/cos75°

We know that sin ( 90°-Ø)=cos Ø
And cos(90°-Ø)=sinØ

=>3(sin39°)/sin39° - 2(cos75°)/cos75°
=3-2
=1

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Hope it helps!!