Q. 5 G5.0( 1 Vote )

# Prove the following :cos90° = 1 – 2 sin245° = 2cos245° – 1

We know that

cos(90o) = 0

taking LHS = cos 90° = 0

Now solving RHS 1- 2sin2 45°

= 1- 1

= 0

= RHS

Now, solving RHS = 2cos2 45° - 1 , we get

= 1- 1

= 0

Hence, proved.

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