Question

задание (b) вычислить ​

Answer 1

Ответ:

= 6/19

Объяснение:

tg a =3

tg a =sin a / cos a

sin a /cos a =3, =>

sin a =3 cos a

(sin^2 a -3 cos^ a )/(2sin^2 a +cos^2 a )=

=((3 cos a )^2-3 cos^2 a )/(2×(3cos a )^2+cos^2 a )=

=(9cos^2 a -3 cos^2 a )/(2×9 cos^2 a + cos^2 a )=6 cos^ a /19 cos^2 a =6/19