Posted by Haley on Wednesday, November 28, 2012 at 9:47pm.
did you notice that 345 = 360-15 ?
cos(345)
= cos15
cos15 = cos(45-30)
= cos45cos30 + sin45sin30
= (√2/2)(√3/2) + (√2/2)(1/2)
= ( √6 + √2)/4
cos 345 = (√6+√2)/4
Related Questions
Pre-Calc - Could someone show me how to solve these two problems-I have 10 of ...
Math, Pre-Calc - the original problem was: Solve: sin(3x)-sin(x)=cos(2x) so far ...
Pre Calc - use properties of the trigonometric function to find the exact value ...
pre-calc help !!!!!!! - #1 cos x+sec x=2 #2 (1+tan x)^2= 2 tan x+2 #3 cos^2x-sin...
pre-calc - Solve: cos(2x-180) - sin(x-90)=0 my work: cos2xcos180 + sin2xsin180= ...
Pre-Algebra - Can someone show me how to solve this problem step by step?Here is...
Pre Calculus - Can someone help me solve this problem: cos^2x + 5cosx - 2= 0 I ...
Calculus - Seperable Equations - Solve the separable differential equation (dy/...
Pre-Calc - I'm so stuck-this stuff is so far above me right now-Please help...
pre-calc helpppp - Find sin x/2, cos x/2, and tan x/2 from the given information...
For Further Reading
