SOLUTION: Can someone please help me with this problem? Even after using the equation correctly, the results aren't right. If sin(x)=(7/8), x in quadrant I, then find (without finding x)

Algebra ->  Trigonometry-basics -> SOLUTION: Can someone please help me with this problem? Even after using the equation correctly, the results aren't right. If sin(x)=(7/8), x in quadrant I, then find (without finding x)       Log On


   

Question 607037: Can someone please help me with this problem? Even after using the equation correctly, the results aren't right.
If sin(x)=(7/8), x in quadrant I, then find (without finding x)
sin(2x)=
cos(2x)=
tan(2x)=
Thank you!
Answer by richard1234(7193) About Me  (Show Source):
You can put this solution on YOUR website!
Use the double-angle formulas.



Here you need to find cos x. Since sin x = 7/8 and then (note that cos x > 0)

Plug everything in to obtain

Finding cos x is fairly simple. Use the identity and replace sin x with 7/8.

Finding tan x is even simpler. Since tan x = (sin x)/(cos x), use the results you found in the previous two parts to find tan x.