Let cos A = with A in QI and find sin(2A)

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  sin(2A) = 0.6

Step-by-step explanation:

A couple of trig identities are involved:

  sin(α) = √(1 -cos(α)²)

  sin(2α) = 2sin(α)cos(α)

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First, we need to find sin(A):

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Alternate solution

Your calculator can also find this for you:

  sin(2A) = sin(2·arccos(1/√10)) = 0.6

a reflection across the x-axis , followed by the by a reflection across the y-axis , and then a scale dilation of 0.5 .

not only in mathematics, scientific proof also are required in the other field of science. also maths proofs are of particular structure, containing steps and logics. so proving is like doing science, it is science. that's why it is important to prove. 

an inaccurate proof leads to errors, or stating results that are not accurate.  which wil mess the probelm up you dont want this