Question

help me..............

Answer 1

Hi !

Solution :-

From LHS

=> 2cos²¢ + 3cos¢ = 2

=> 2cos²¢ + 3cos¢ - 2 = 0

=> 2cos²¢ + 4cos¢ - cos¢ - 2 = 0

=> 2cos¢ ( cos¢ + 2) - 1 ( cos¢ + 2) = 0

=> (2cos¢ - 1) ( cos¢ + 2) =0

cos¢ + 2 = 0

cos¢ = - 2 ( neglecting )

now ,

=> 2cos¢ - 1 = 0

=> cos¢ = 1 /2

since , cos¢ = cos60°

¢ = 60 °

Hence, cos3¢ = cos3 * 60 ° = cos180° = 0

since , cos3¢ = 0 Answer ✔

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Hope this helps !!

@Rajukumar111