[tex]\displaystyle\bf\\1)~~Adevarat~deoarece~unghiul~obtuz~este~in~cadranul~2.\\\\2)~~0,45^o=\Big(\frac{45}{100}\Big)^o=\frac{x}{60} \\\\x=\frac{45\cdot60}{100}=27' (minute~de~grad)\\\\\implies~~39,\!45^o=39^o27'\\\\\implies~2)~(adevarat)\\\\3)~~De finitie~incompleta.\\\\Unghiul~nul~este~unghiul~ale~carui~laturi~sunt~doua~semidrepte\\care~pleaca~din~acelasi~punct~in~aceeasi~directie~si~se~suprapun.\\\\4)~~Cercul~are~o~infinitate~de~axe~de~simetrie~NU~doar~4.[/tex]