Question

sin 3x == cos 18 degree find the value of x​

Answer 1

Answer:

cos(2x) = sin(3x)

so

cos(2x) = sin(x)cos(2x) + cos(x)sin(2x)

or

cos(2x)- sin(x)cos(2x) = cos(x)(2sin(x)cos(x))

cos(2x)[1 - sin(x)] = 2cos2(x)sin(x) = 2[1 - sin2(x)] sin(x)

Hence

cos(2x)[1 - sin(x)] = 2[1 - sin(x)][1 + sin(x)] sin(x)

and thus

cos(2x) = 2 [1 + sin(x)] sin(x)

Note: You need to check that sin(x) = 1 is not a solution to the original problem.

Finally

1 - 2 sin2(x) = 2 sin(x) + 2 sin2(x)

or

4 sin2(x) +2 sin(x) - 1 = 0

Solve for sin(x).

Andrei, Claude and Penny

Answer 2

Step-by-step explanation:

Here's your answer

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