Posted by **george** on Monday, January 11, 2010 at 1:01am.

Given tanu= -1/3 and sinu <0, find sin(u/2)

if 0 is less than or equal to u < 2 pie

I think its a right triangle in fourth quadrant with the point (3,-1) (hypotenuse equals square root of ten) but I'm brain dead and can't find u or any solutions.

- precalculus half angle question stumped -
**drwls**, Monday, January 11, 2010 at 1:38am
I assume you want to solve for u, not a triangle. Tan u is negative in the second and fourth quadrant, and sie u is negative in the third and fourth, therefore you are correct that u must be in the fourth quadrant. The reference angle (which it makes with the +x axis is arctan 1/3.) You are correct that a line between (3, -1) and the origin will make an agle u with the x axis. That angle is 18.435 degrees and the angle u is 341.565 degrees

## Answer This Question

## Related Questions

- math - tan (u-v) given sin u=3/4 and cos v= -5/13 with U and V in quadrant 2 Use...
- Precalculus troubles - If sinu= (-5/7) and pie<u< (3pie/2) find sin 2u
- Math (Precalculus) - I have no idea how to do these problems: Given that U and V...
- math (trig) - Find sin(x/2) if sin(x)= -0.4 and 3pi/2 < or equal to (x) < ...
- trig help - I need help finding sinA if cosA=(-3/5) and A is greater than 90 ...
- PLEASE HELP!!!!! (Right Triangle Question) - Point N is on hypotenuse BC of ...
- Trig - how do i find the exact value of s [pie/2, pie] sin s = radical2/ whole ...
- Trigonometry - 4. Find the exact value for sin(x+y) if sinx=-4/5 and cos y = 15/...
- maths - Choose three options which are true: a) an angle of 150 degrees is ...
- inverse trig functions - evaluate the following expressions: tan(sec^-1(5/3)) ...

More Related Questions