M =cosa/cosb , n= cosa/sinb then prove that ( m+n) (m-n) cosSquare b =nsquare

M =cosa/cosb , n= cosa/sinb then prove that ( m+n) (m-n) cosSquare b =

1.	M =cosa/cosb , n= cosa/sinb then prove that ( m+n) (m-n) cosSquare b =nsquare
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