1+sin(-b)/cos(-b)-tg(-b= 1 - sin(b)/cos(b) - tan(b= 1 - tan(b) - tan(b= 1 - 2tan(b)
cos^2(-b)-cos^4(-b)/sin^2(-b= cos^2(b) - cos^4(b)/sin^2(b= cos^2(b)(1 - cos^2(b))/sin^2(b= sin^2(b)/sin^2(b= 1
cos(-a)/1+sin(-a)+tg(-a= cos(a) / (1 - sin(a) + tan(a)= cos(a) / (1 - sin(a) + sin(a)/cos(a)= cos^2(a) / cos(a= cos(a)
1+sin(-b)/cos(-b)-tg(-b
= 1 - sin(b)/cos(b) - tan(b
= 1 - tan(b) - tan(b
= 1 - 2tan(b)
cos^2(-b)-cos^4(-b)/sin^2(-b
= cos^2(b) - cos^4(b)/sin^2(b
= cos^2(b)(1 - cos^2(b))/sin^2(b
= sin^2(b)/sin^2(b
= 1
cos(-a)/1+sin(-a)+tg(-a
= cos(a) / (1 - sin(a) + tan(a)
= cos(a) / (1 - sin(a) + sin(a)/cos(a)
= cos^2(a) / cos(a
= cos(a)