Prove that cos9plus sin9divide by cos 9minus sin 9is equal to tan 54
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cos 9 + sin 9/ cos 9 - sin9
Divide numerator and denominator by cos 9
we get
1 + tan9/ 1 - tan9
tan45 + tan9 / 1 - tan45×tan9 (as tan45= 1)
tan(45+9)= tan54 .
as tan(a+b) = tan a + tan b/1- tan a × tan b
Divide numerator and denominator by cos 9
we get
1 + tan9/ 1 - tan9
tan45 + tan9 / 1 - tan45×tan9 (as tan45= 1)
tan(45+9)= tan54 .
as tan(a+b) = tan a + tan b/1- tan a × tan b
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