Question

найти tgалфа если sinалфа=-21/29 и 3π/2< алфа<2π​

Answer 1

Ответ:

$sina=-\dfrac{21}{29}\\\\\\cos^2a=1-sin^2a=1-\dfrac{441}{841}=\dfrac{400}{841}\ \ \ \Rightarrow \ \ \ cosa=\pm \dfrac{20}{29}\\\\\\\dfrac{3\pi }{2}<a<2\pi \ \ \ \ \Rightarrow \ \ \ cosa>0\ \ \ \Rightarrow \ \ \ cosa=+\dfrac{20}{29}\\\\\\tga=\dfrac{sina}{cosa}=\dfrac{-\frac{21}{29}}{\frac{20}{29}}=-\dfrac{21}{20}$