# Trig Identity

## Homework Statement

Prove that tanx + 1 = secx.

## Homework Equations

sinx/cosx + 1 = 1/cosx

NascentOxygen
Staff Emeritus
Science Advisor

## Homework Statement

Prove that tanx + 1 = secx.

Have you tried substituting a value, any value, to confirm this may be true?

It will be rather difficult to prove that it's an identity if it really isn't. eumyang
Homework Helper

## Homework Statement

Prove that tanx + 1 = secx.

## Homework Equations

sinx/cosx + 1 = 1/cosx

## The Attempt at a Solution

Check wherever you got this problem from to see if you copied it correctly. It looks like something is missing in the original problem.

Don't you mean tan2x + 1 = sec2x?

I wish I did. I am reviewing precalc with a student as a private tutorto prepare him for H.S. Calc. and this problem was one that neither of us could figure out.

I think you forgot the squares... if you meant them then
start with
sin(x)^2+cos(x)^2=1
Do you have any clue or idea were to go from here?

HallsofIvy
Science Advisor
Homework Helper
What people are telling you is that you cannot prove tan x+ 1= sec x, it is NOT true. For example if x= 45 degrees ($\pi/4$, the left side is 2 while the right side is $\sqrt{2}$.

You can prove that $tan^2 x+ 1= sec^2(x)$ for all x.

I realize that and have come to the conclusion that either I miscopied the problem, the book has a misprint, or we both misunderstood the instructions. Thanks everyone. I will look at the problem at our next session and figure out where to go.