Question

объясните плиз ,а то не пойму

Answer 1

ctg2β*tg2β=1 , ctg2β=1/tg2β , tg2β=2tgβ/(1- tg²β)

1+tg²β=1/cos²β , 1+tg²β=1/(225/289) , tg²β=(289/225)-1 , tg²β=64/225,

tgβ= -8/15.

tg2β=2tgβ/(1- tg²β)= 2*(-8/15)/(1 +64/225)=-16/15:(162/225)=-240/161

ctg2β=1:(-240/161)=-161/240