Posted by Jenn on Sunday, November 8, 2009 at 10:24pm.
Angle x is in the second quadrant and angle y is in the first quadrant such that sinx=5/13 and cosy=3/5, determine and exact value for cos (x+y).
I have no idea how to even start this question. Could someone please help me?

Math  stephanie, Sunday, November 8, 2009 at 10:39pm
x=arcsin(5/13)
y=arccos(3/5)
so find those calculations and plug it into cos(x+y) or in other words
cos(x+y)=(arcsin(5/13)+arccos(3/5))

Math  I still don't understand  Jenn, Sunday, November 8, 2009 at 11:19pm
Well, I understand what you mean by the solution, but I am getting a really long decimal as the answer, so that's not an excat value. Please, can you help me some more?

Math  Reiny, Monday, November 9, 2009 at 8:42am
Make diagrams of your triangles in the corresponding quadrants
if sinx = 5/13 and is in II
then cosx = 12/13
if cosy = 3/5 and is in I
then siny = 4/5
cos(x+y) = cosxcosy  sinxsiny
= (12/13)(3/5)  (5/13)(4/5)
= 56/65
Answer This Question
Related Questions
 trig  Angle x is in the second quadrant and angle y is in the first quadrant ...
 trig  Angle x is in the second quadrant and angle y is in the first quadrant ...
 Math!!!  angle x is in the second quadrant and angel y is in the first quadrant...
 Urgent  draw an angle x in the 1st quadrant with sinx=3/5, and an angle y in ...
 math  Angles x and y are located in the first quadrant such that sinx=3/5 and ...
 PreCal  [Note: This one... is super hard for me :( I really need help. please...
 advanced functions  Angles x and y are located in the first quadrant such that ...
 Trig  The angle 2x lies in the fourth quadrant such that cos2x=8/17. 1.Which ...
 maths  Angle a lies in the second quadran and angle b lies in the third ...
 pre calc  Find the exact value of sin(xy) if sinx=3/5 in Quadrant III and ...
More Related Questions