ГДЗ по геометрии 9 класс Мерзляк Задание 7

\[\mathbf{Найдем\ }\mathbf{ко}\mathbf{синус.}\]

\[1)\sin a = 1:\]

\[\cos^{2}a = 1 - \sin^{2}a = 0\]

\[\cos a = \pm \sqrt{0} = 0.\]

\[2)\sin a = 0:\]

\[\cos^{2}a = 1 - \sin^{2}a = 1\]

\[\cos a = \pm \sqrt{1} = \pm 1.\]

\[Найдем\ котангенс.\]

\[1)\ tg\ a = - 1:\]

\[ctg\ a = \frac{1}{\text{tg\ a}} = - 1.\]

\[2)\ tg\ a = 3:\]

\[ctg\ a = \frac{1}{\text{tg\ a}} = \frac{1}{3}.\]