Tan155degree-tan155degree/1+tan155degree.tan155 degree=1-a^2/2a
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By using the formula =tanA+tanB=tanA-tanB/1+tanAtanB
LHS,
tan155°-tan155°/1+tan155°tan155°=
tan(155°+155°)
=>tan2(155°)
we know that, tan2A=2tanA/1-tan²A
tan2(155°)= 2tan155°/1-tan²155°
take tanA as 1/cotA
then, 1/cot2(155°)=1/2cot155°/1/1-cot²155°
1/cot2(155°)=1-cot²155°/2cot155°
put the calue of cot155°=a
then., 1-a²/2a
hence RHS=LHS
LHS,
tan155°-tan155°/1+tan155°tan155°=
tan(155°+155°)
=>tan2(155°)
we know that, tan2A=2tanA/1-tan²A
tan2(155°)= 2tan155°/1-tan²155°
take tanA as 1/cotA
then, 1/cot2(155°)=1/2cot155°/1/1-cot²155°
1/cot2(155°)=1-cot²155°/2cot155°
put the calue of cot155°=a
then., 1-a²/2a
hence RHS=LHS
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