matematika.. tolong dibantu

jawab

tan 1/8π = -1 + √2

(2 tan 1/8 π )/ (1 - 5 tan²  1/8 π) = 

= 2 ( - 1 + √2 ) / ( 1 - 5 (-1 +√2)²)

= 2 ( -1 + √2 ) / ( 1 - 5 (3- 2√2))

= 2 ( - 1 + √2) / ( 1- 15 +10√2 )

= 2 ( - 1 +  √2 ) / (-14 + 10 √2) 

= 2 ( -1 + √2) /  2 (-7 + 5 √2)

= (-1 + √2)/( -7 + 5 √2)

= ( -1 + √2)(- 7 - 5√2)  / (-7 + 5√√2)(-7 - 5√2)

= (-1 + √2)(-7 - 5√2) / (49 - 50)

= (7 - 2√2 -10) / (- 1)

=  (- 3 - 2√2) / (-1)

= 3 + 2√2