Question 349045
sec(77)^2-tan(77)^2=1/cos(77)^2-sin(77)^2/cos(77)^2 | def. of sec and tan
 
=(1-sin(77)^2)/cos(77)^2 
 
=cos(77)^2/cos(77)^2 | cos^2+sin^1=1 trig. identity
 
=1.