SOLUTION: Without using a caculator, Find cos x/2, given cot x = (-3), with the sign of pie/2 < x < the sign of pie.
Algebra ->
Trigonometry-basics
-> SOLUTION: Without using a caculator, Find cos x/2, given cot x = (-3), with the sign of pie/2 < x < the sign of pie.
Log On
Question 293867: Without using a caculator, Find cos x/2, given cot x = (-3), with the sign of pie/2 < x < the sign of pie. Answer by Alan3354(69443) (Show Source):
You can put this solution on YOUR website! Without using a caculator, Find cos x/2, given cot x = (-3), pi/2 < x < pi
------------------------
Plot the point (-3,1)
The angle from the Origin is angle x, and is in the 2nd quadrant.
The hypotenuse is sqrt(10), so the cos(x) = -3/sqrt(10) = -3sqrt(10)/10
----------------
Use the half-angle formula:
cos(x/2) = sqrt(2+2cos(x))/2
