Question #d5176

Question

223 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2018-01-06T20:22:40

See below.

LHS:

Identity:

#color(red)(sec^2x=1+tan^2x)#

#1+tan^2x-tan^2x#

#1#

#1=cosx#

#sec^2x-tan^2x=cosx# is an equation.

This could also be determined by looking at #sec^2x#:

#sec^2(x)=1/cos^2x# This is undefined if #cos^2x=0#

An identity must be true for all values of the variable.