tg ⁡ ( A ± B ) = tg ⁡ A ± tg ⁡ B 1 ∓ tg ⁡ A tg ⁡ B . {\displaystyle \mathop {\operatorname {tg} } (A\pm B)={\frac {\mathop {\operatorname {tg} } A\pm \mathop {\operatorname {tg} } B}{1\mp \mathop {\operatorname {tg} } A\ \mathop {\operatorname {tg} } B}}.}