Ctg^2альфа , если 88sin^2альфа -90cos^2альфа =10

Question

Ctg^2альфа , если 88sin^2альфа -90cos^2альфа =10

Answer 1

1) 88sin^2a -90cos^2a =10 => 88sin^2a-90(1-sin^2a)=10 => 88sin^2a-90+90sin^2a=10 => 178sin^2a=100 => sin^2=100/178; 2) 1+ctg^2a=1/sin^2a => ctg^2a=1/sin^2a-1 => ctg^2a=178/100-1=0,78