# Homework Help: Trig Test Question

1. Dec 17, 2008

### ruthless

1. The problem statement, all variables and given/known data
tana^2 = sin2a

2. Relevant equations

3. The attempt at a solution
i set tana^a = sec^2a -1
sec^2 -1 = 2sinacosa

didnt know where to go from here <_<

Last edited: Dec 17, 2008
2. Dec 17, 2008

### sutupidmath

do u want to show that $$tan(a^2)=sin(2a)$$ or what?
and also is the problem like i wrote here or it should be sth like this:$$(tana)^2=sin(2a)$$

??

p.s use more parentheses they don't hurt.

3. Dec 17, 2008

### ruthless

its the second way
$$(tana)^2=sin(2a)$$
and i need to find values for x
for example pi/4 pi/6 answers wont be like that but yea
its not a proof

4. Dec 17, 2008

### jgens

Alright, if you're aiming for solutions, try rearranging/reexpressing the equation so it satisfies the zero product property.

Hint: reexpress (tan(a))^2 in terms of sine and cosine, and reexpress the sin(2a) in terms of cos(a) and sin(a).

5. Dec 17, 2008

### ruthless

well i did
didnt work
trust me ive been on this for an hour and yeah ive tried to set it equal to zero

6. Dec 17, 2008

### jgens

It should be fairly simple if you're familiar with elementary algebraic operations. You need to show what you're trying if you want help.

7. Dec 17, 2008

### ruthless

well ok
i did
sinx^2/cosx^2 = 2sinxcosx
then brign right hind side to left hand side, at the end it comes out to be
sinx^2 - 2sinxcosx^3 = 0
then sin facotrs and sin x = 0
but im still left with sinx - 2cos^3x

8. Dec 17, 2008

close SOLVED