Posted by **Bailey ** on Monday, January 11, 2010 at 9:12pm.

I can't remember what formula to use for these.

Note- the X's may be replaced by a theta symbol. I just didnt have one on my keyboard.

Use the given information to find sin2X, cos2X and tan2X if 0< X <pi/2

1. sinX=12/13

2. cosX=3/5

3. tanX=2/3

- Trigonometry -
**Diana**, Monday, January 11, 2010 at 9:37pm
You use the double angle formulas.

- Trigonometry -
**MathMate**, Tuesday, January 12, 2010 at 7:30am
To type θ, you need to type the following without the double quotes nor the spaces: "& t h e t a ;".

As Diana suggested, use the double angle formulas. I'll do the first one as an example.

sin(2θ)

=2sin(θ)cos(θ)

sin(&theta)=12/13

cos(&theta)=sqrt(1²-(12/13)²)=5/13

Therefore

sin(2θ)

=2sin(θ)cos(θ)

=2(12/13)(5/13)

=120/169

## Answer This Question

## Related Questions

- Maths- complex numbers - Find tan(3 theta) in terms of tan theta Use the formula...
- Trigonometry - I don't understand how I'm supposed set the problem up or what ...
- trigonometry - if sin2x=3sin2y, prove that: 2tan(x-y)=tan(x+y) ( here, in sin2x...
- Trigonometry - Okay, I have been given a trigonometric equation to solve (sin^2(...
- Trigonometry - A batter hits a ball with an initial velocity v0 of 100 feet per ...
- dma 040 - Substitute the given values into the given formula and solve for the ...
- Trigonometry - 1. sin^2 theta+cos theta=2 (Hint: Use the Pythagorean identity ...
- pre algebra - write an equation for the line through the given points or through...
- Trigonometry - Use a sum of difference identity to write the expression as a ...
- Pre-Cal: Domain - [Note: I really need help on these Domain questions. I've been...

More Related Questions