Question

cos36 cos 54- sin 36 sin54=?

Answer 1

=Cos(90-54) cos54 - sin36 sin(90-36)
=Sin36 Cos54 - Sin36 Cos54
=0



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Answer 2

Answer:

$cos36 cos54-sin36sin54=0$

Step-by-step explanation:

$we\:know\: that,\\\boxed {cosAcosB-sinAsinB = sin(A+B)}$

$cos36 cos54-sin36sin54\\=cos(36+54)\\=cos90\degree\\=0$

Therefore,

$cos36 cos54-sin36sin54=0$

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