Math Is Fun Forum

BonaviaFx

Member

Registered: 2014-12-15

Posts: 11

Trigonometric Identities Problem

I'm Stuck on this one:

tan^2x-sin^2x ≡ sin^4x*sec^2x

Need some help

Last edited by BonaviaFx (2015-01-09 09:24:56)

Bob

Administrator

Registered: 2010-06-20

Posts: 10,140

Re: Trigonometric Identities Problem

hi BonaviaFx

I just give the hints so you can finish this yourself. 

tan = sin/cos so use this to 'remove' the tan and factorise a sin term.

When you factorise, the remaining bracket needs to be over a single denominator.

Then sin^2 = 1 - cos^2 will enable you to simplify what remains.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

BonaviaFx

Member

Registered: 2014-12-15

Posts: 11

Re: Trigonometric Identities Problem

How about from the RHS:

RHS=Sin^2xSin^2xSec^x

(1-Cos^2x)Sin^2x(1/Cos^2x)

(Sin^2x/Cos^2x)-(Cos^2xSin^2x/Cos^2x)

Tan^2x-Sin^2x

Correct?

I Used the RHS because I still didn't manage from the LHS.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,140

Re: Trigonometric Identities Problem

hi BonaviaFx

Yes, That looks ok to me. 

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

BonaviaFx

Member

Registered: 2014-12-15

Posts: 11

Re: Trigonometric Identities Problem

Thanks