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(cos9^@+sin9^@)/(cos9^@-sin9^@)= (a) tan...

`(cos9^@+sin9^@)/(cos9^@-sin9^@)=` (a) `tan 54^@` (b) `tan 36^@` (d) None of these (c) `tan18^@`

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LHS=`(cos9^@+sin9^@)/(cos9^@-sim9^@)`
Dividing numerator, and denominator by` cos9^o`,
we get
=`(1+tan9^@​)/(1−tan9^@)`
=`(tan45^@+tan9^@)/(1−tan45^@tan9^@)`
=`tan(45^@+9^@)=tan54^@=`
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