Posted by **nik** on Wednesday, April 10, 2013 at 12:42pm.

GIVEN THE ANGEL ALFA WITH COS ALFA = -1/a. IF ALFA IN QUADRANT TWO, THE VALUE OF SIN ALFA IS....

- trig -
**Steve**, Wednesday, April 10, 2013 at 12:47pm
since sin^2 + cos^2 = 1,

sin^2 = 1 - cos^2 = 1-(1/a^2)

so sin = √(1 - 1/a^2) = 1/a √(a^2-1)

to see this, draw your triangle and label the adjacent leg=1 and the hypotenuse=a. Then the other leg is √(a^2-1) and the sin is just √(a^2-1)/a.

Since sin > 0 in QII, that's the value; no - sign needed. in fact, if you draw the angle in QII, you will see that's so, since sin=y/r and y>0.

## Answer This Question

## Related Questions

- math - (1)given that -2x^2+6x+7=0, if alfa and B are the roots of the equation, ...
- math-trigon. - [1-sin^2(alfa+beta)]/cos^2(alfa+beta)
- math - prove alfa+Bita=90 degree,show the maximum value of cos alfa cos bita is ...
- math - If alfa and bita are the zeroes of x square plus px plus of then find the...
- math - If alfa and bita are zeroes of poly x square minus 3x plus 2 then find ...
- Pre-Calculus - An Alfa Romeo going at 70 mph requires 169 feet to stop. Assuming...
- Geometry - ABCA1B1C1 is a prism which has regular triangles in the bases. The ...
- calculus - According to Car and Driver, an Alfa Romeo going 70 mph requires 177 ...
- Calculus - According to Car and Driver, an Alfa Romeo going 70 mph requires 177 ...
- 11th grade - ABCA1B1C1 is a prism which has regular triangles in the bases. The ...

More Related Questions