Question

math. help me to solve this question
prove the above ☝

Answer 1

convert cos9 = sin81 and use sin c + sin d
and in denominator convert sin 9 into cos 81 and use cos c - cos d formula u will get ur answer

Answer 2

54°-9°=45°

or, 54°=45°+9°

or, tan54°=tan(45°+9°)

or, tan54°=tan45°+tan9°/1-tan45°tan9°

or, tan54°=1+tan9°/1-tan9° [∵, tan45°=1]

or, tan54°=(1+sin9°/cos9°)/(1-sin9°/cos9°)

or, tan54°={(cos9°+sin9°)/cos9°}/{(cos9°-sin9°)/cos9°}

or, tan54°=cos9°+sin9°/cos9°-sin9° (Proved)