0\; ,\; \; tga<0\; ,\; \; ctga<0\\\\cosa=+\sqrt{1-sin^2a}=\sqrt{1-\frac{40^2}{41^2}}=\sqrt{\frac{81}{41^2}}=\frac{9}{41}\\\\tga=\frac{sina}{cosa}=-\frac{40}{41}:\frac{9}{41}=-\frac{40}{9}=-4\frac{4}{9}\\\\ctga=\frac{1}{tga}=-\frac{9}{40}" alt="sina=-\frac{40}{41}\; ,\\\\\frac{3\pi }{2}<a<2\pi \; \; \Rightarrow \; \; cosa>0\; ,\; \; tga<0\; ,\; \; ctga<0\\\\cosa=+\sqrt{1-sin^2a}=\sqrt{1-\frac{40^2}{41^2}}=\sqrt{\frac{81}{41^2}}=\frac{9}{41}\\\\tga=\frac{sina}{cosa}=-\frac{40}{41}:\frac{9}{41}=-\frac{40}{9}=-4\frac{4}{9}\\\\ctga=\frac{1}{tga}=-\frac{9}{40}" align="absmiddle" class="latex-formula">