SOLUTION: Find sin x given sec x = -4 and sin x < 0 I know that it's in Quadrant 3 but I don't know how to plug in the numbers on the triangle and how to put the numbers in the formula

Algebra ->  Trigonometry-basics -> SOLUTION: Find sin x given sec x = -4 and sin x < 0 I know that it's in Quadrant 3 but I don't know how to plug in the numbers on the triangle and how to put the numbers in the formula      Log On


   

Question 1024522: Find sin x given sec x = -4 and sin x < 0
I know that it's in Quadrant 3 but I don't know how to plug in the numbers on the triangle and how to put the numbers in the formula
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
sec%28x%29=-4
1%2Fcos%28x%29=-4
cos%28x%29=-1%2F4
You know that,
sin%5E2%28x%29%2Bcos%5E2%28x%29=1
sin%5E2%28x%29%2B%28-1%2F4%29%5E2=1
sin%5E2%28x%29%2B1%2F16=1
sin%5E2%28x%29=15%2F16
sin%28x%29=0+%2B-+sqrt%2815%29%2F4
So,
sin%28x%29=-sqrt%2815%29%2F4