SOLUTION: sin^-1 (3÷5) + sin^-1 (5÷13) = sin^-1 (56÷65)

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Question 1011508: sin^-1 (3÷5) + sin^-1 (5÷13) = sin^-1 (56÷65)
Answer by ikleyn(52873)   (Show Source): You can put this solution on YOUR website!
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sin^-1 (3÷5) + sin^-1 (5÷13) = sin^-1 (56÷65)
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Thus we need to prove that  arcsin + arcsin = arcsin.

Proof

Let  = arcsin and  = arcsin.

Thus  =  and  is in Quadrant 1;    =  and  is in Quadrant 1 also.

We need to prove that  =   and   +  is in Quadrant 1.

Since  = , you have  =  =         (make all intermediate calculations yourself)

Since  = , you have  =  =     (make all intermediate calculations yourself)

Now apply the formula for :

 =  =  =  = .   

Thus the first half of the statement is proved.

Next calculate :

 =  =  =  = .

Since  > 0,  is in the quadrant 1.

The proof is completed.


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