[tex]0,25-cos^{2}(x)=0\\ cos^{2}(x)=0,25\\cos(x)=0,5\\x=\pi/3 + 2k\pi\\x=-\pi/3 + 2k\pi\\k=1,2,3...[/tex]
[tex]3tan^{2}(x)-\frac{1}{cos^{2}(x) }=5\\3\frac{sin^{2}(x) }{cos*{2}(x)}-5\frac{cos^{2}(x) }{cos^{2}(x)}=0\\3 sin^{2}(x)-1-5(1- sin^{2}(x))=0\\8sin^{2}(x)=6\\sin^{2}(x)=6/8\\\\sin(x)=\frac{\sqrt{3}}{2}\\x=\frac{\pi }{3} + 2k\pi\\ x=\frac{2\pi }{3} + 2k\pi\\k=0,1,2....[/tex]
