The line with equation a + 2b = 0 coincides with the terminal side of an angle θ in standard position and cos θ<0.

What is the value of sinθ?

−2√5/5

√5

−1/2

√5/5

Guest Dec 8, 2017

#1**+2 **

1a + 2b = 0

2b = -1a

b = (-1/2)a

The slope of this line is (-1/2)....this line lies in the II and IV quadrants...and since the cos < 0, then this must be a II quadrant angle so the sine must > 0

So.....find r = √ [ x^2 + y^2 ] = √ ] (-2)^2 + (1)^2 ] = √5

So....the sinθ = 1/ √5 = √5 / 5

CPhill
Dec 8, 2017