Question

evaluate 2 cos square 15 degree minus one​

Answer 1

Answer:

0.866312

Step-by-step explanation:

cos 15 degree = 0.96593 = 0.966

so, cos square 15 degree = cos 15 * cos 15 = 0.966*0.966 = 0.933156

so, 2 cos square 15 degree minus one means =

2*cos^2(15 degree) -1

=(2*0.933156) - 1

= 1.866312 - 1

= 0.866312

Answer 2

2cos²15° - 1 = √3/2

Given :

The expression 2cos²15° - 1

To find :

Simplify the expression

Formula :

2cos²θ - 1 = cos 2θ

Solution :

Step 1 of 2 :

Write down the given expression

The given expression is

2cos²15° - 1

Step 2 of 2 :

Simplify the given expression

We are aware of the Trigonometric formula that

2cos²θ - 1 = cos 2θ

Now taking θ = 15° we get

2cos²15° - 1

= 2cos²θ - 1

= cos 2θ

= cos ( 2 × 15° )

= cos 30°

= √3/2

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