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\frac { \operatorname { cos } 36 - \operatorname { sin } 36 } { \operatorname { cos } 36 + \operatorname { sin } 36 } |
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Answer» we have (cos x - sin x)/( cos x + sin x)= (1- sin x/ cos x)/(1+ sin x/ cos x)= (1- tan x)/ ( 1+ tan x)= tan (45-x) as tan (45-x) = (tan 45 - tan x)/((1+ tan 45 tan x) = (1- tan x)/(1+ tan x) putting x = 36 we get (cos36-sin36)/(cos36+sin36)= tan (45-36)= tan 9 = tan (180+9) = tan 189 how uh did d 2nd step |
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