tan^2x+sec^2x=1 true or false? for ALL values of x

Question

tan^2x+sec^2x=1 true or false? for all values of x

 

2) cos2a=2cos^2a-1

for ALL values of a 

true or false? 

 

3) sin(-x)=-sinx for all values of x

true or false? 

 

 

Answer 1

1) False, 1 + tan²x = sec²x

 

2) True

 

3) True