([email protected][email protected])^2-(ctg-tg)^2

[email protected]^[email protected]^[email protected]@-([email protected]^[email protected]^[email protected]@= [email protected]^[email protected]^[email protected]@[email protected]^2 [email protected]^[email protected]@= [email protected]@= 4 ([email protected]×[email protected]=1 по формуле)