Posted by **kathleen** on Monday, December 6, 2010 at 3:50pm.

I am stuck on a problem that has to do with the double angle formulas. I have to solve this: 4sinxcosx = 1. I tried using the formula 2sinu = 2sinucosu by substituting it in like this: 2(2sinxcosx)= 1 but then I am stuck

- Math -
**Reiny**, Monday, December 6, 2010 at 4:51pm
remember that sin 2x = 2sinxcosx

so 4sinxcosx = 1

2(2sinxcosx) = 1

2(sin2x) = 1

sin2x = 1/2

I will assume you are working in degrees, we can always switch later on

so 2x = 30° or 2x = 150° because of the CAST rule

x = 15° or x = 75°

the period of sin 2x is 180°, so adding 180 to any answer will produce new answers

x = 15°, 195°, ...

or

x = 75°, 255°, ...

In Radians:

15° = π/12 radians

x = π/12, 13π/12....

x = 5π/12, 17π/12, ...

## Answer this Question

## Related Questions

- Precalculus - I've tried many times to get the equation to balance using trig ...
- math - sin2x-cotx = -cotxcos2x Using the various trigonometric identities(i.e. ...
- Math 2nd question - Express as a single sine or cosine function (note: this is ...
- Math Word Problem - As payment for his daughters yard work, a father agrees to ...
- math,help - i am stuck with this problem: Problem #12 Solve by using the ...
- math - 1. 4x^2-13x=12 I need to solve this problem by factoring or using the ...
- Trig/Precalc - So I have two questions that have been puzzling me for quite some...
- MATH - 1.)Find the exact solution algebriacally, if possible: (PLEASE SHOW ALL ...
- Calculus - Solve the first-order initial value problem using half angle formulas...
- Physics - A track star in the long jump goes into the jump at 12 m/s and ...

More Related Questions