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Problem 15

Posted in Math Problems by Lia on 06/02/2011

Given:

{{sin(x + z)}/{sin(y - z)}} = m and  {{cos(x - z)}/{cos(y + z)}} = n

Show that the identity:

{{cos{2z}}/{cos(x - y)}} = {{m + n}/{mn + 1}}

is true.

Admission exam to Engineering,

Polytechnic Institute of Bucharest, Romania, 19xx

Our Translation.

 
 

Hint

Our Solution

 

 

 

 

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