Question

Prove it without using trigonometric tables :
$cos54 cos36 - sin54 sin36 = 0$




plz help fast.........​

Answer 1

Answer:

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$cos54 cos36 - sin54 sin36 = 0$

cos 54 = cos (90 - 36)

cos 36 = cos ( 90 - 54 )

now substitute

cos ( 90 - 36 ) . cos ( 90 - 54 ) - sin 54 . sin 36

we know that cos 90 - theta = sin theta

sin 36 . sin 54 - sin 54 . sin 36

= 0

hope it helps

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Answer 2

Answer:

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