Question

$frac{tg^2 1.8-tg^21.2}{1-tg^21.8*tg^2 1.2}$

Answer 1

Ответ:  (tg0,6)*(tg3 ) .

Объяснение:  

* * * tg(α+β) =(tgα+tgβ) /(1 - tgα+tgβ) ; tg(α-β) =(tgα-tgβ)/(1 + tgα+tgβ) * * *

( tg²1.8 - tg²1.2 ) / ( 1 - tg²1.8 *tg²1.2 ) = ( tg²1.8 - tg²1.2 ) / ( 1 - (tg1.8 *tg1.2)² ) =

( tg1.8 - tg1.2 ) ( tg1.8 + tg1.2 ) / ( 1 +tg1.8 *tg1.2 )(1 - tg1.8* tg1.2) =

( ( tg1.8 - tg1.2 ) / ( 1 +tg1.8 *tg1.2 ) ) *( ( tg1.8 + tg1.2 ) / ( 1 - tg1.8 *tg1.2 ) ) =

= tg(1.8 - 1.2 ) * tg(1.8 + 1.2 ) =(tg0,6)*(tg3 ) .