[tex]\Large\boxed{\begin{array}{l}\rm 1)\\\begin{array}{c|c|c|c|c|c}\sf a&\sf0^\circ&\sf90^\circ&\sf180^\circ&\sf270^\circ&\sf360^\circ\\\sf sen(a)&\sf0&\sf1&\sf0&\sf-1&\sf0\\\sf cos(a)&\sf1&\sf0&\sf-1&\sf0&\sf1\\\sf tg(a)&\sf0&\sf\not\!\exists&\sf0&\not\!\exists&\sf0\end{array}\end{array}}[/tex]
[tex]\Large\boxed{\begin{array}{l}\rm 2)\\\sf se~tg(a)=1\implies\dfrac{sen(a)}{cos(a)}=1\\\sf portanto~sen(a)=cos(a),\\\sf onde~a~pertence~aos~quadrantes~I~e~III\\\huge\boxed{\boxed{\boxed{\boxed{\sf\red{\maltese}~\blue{alternativa~d}}}}}\end{array}}[/tex]
[tex]\Large\boxed{\begin{array}{l}\rm 3)\\\begin{array}{c|c|c|c|c|c|c|c}\sf a&\sf15^\circ&\sf115^\circ&\sf196^\circ&\sf290^\circ&\sf178^\circ&\sf81^\circ&\sf267^\circ\\\sf sen(a)&\sf+&\sf+&\sf-&\sf-&\sf+&\sf+&\sf-\\\sf cos(a)&\sf+&\sf-&\sf-&\sf+&\sf-&\sf+&\sf+\\\sf tg(a)&\sf+&\sf-&\sf+&\sf-&\sf-&\sf+&\sf-\end{array}\end{array}}[/tex]
