The discussion revolves around the equivalence of the expression cos(∏/2 + x) - cos(∏/2 - x) and its simplification using trigonometric identities, specifically the sum and difference formulas for cosine.
Several participants are actively engaging with the problem, attempting to apply the relevant formulas while questioning their understanding of the angle assignments. Guidance has been offered regarding the separation of the formulas for each part of the expression, but there remains some uncertainty about the application and interpretation of the formulas.
Participants note that they are working within the constraints of a homework assignment, which may limit their approach to the problem. There is also mention of a lack of clarity from previous instruction regarding the application of the formulas.
keishaap said:Homework Statement
Which is equivalent to: cos(∏/2 + x) - cos(∏/2 - x)?
A) -2cos(x)
B) -2
C) 0
D)-2sin(x)
Homework Equations
Cos (A-B)
The Attempt at a Solution
I am totally stuck :( please help!
Dick said:You mentioned the sum and difference formulas. I think you should try to use them.
keishaap said:I have tried to use them but i totally get stuck like i don't know which is a or b and we are only given cos (a-b) = cosAcosB + sinAsinB
keishaap said:Cos (pi/2) =0
Sin(pi/2)= 1
keishaap said:I have tried to use them but i totally get stuck like i don't know which is a or b and we are only given cos (a-b) = cosAcosB + sinAsinB
keishaap said:How come the b is not a -x ?
Dick said:Why would you think that?? If you have a formula for cos(a-b) and you want to apply it to cos(pi/2-x) then you should put a=pi/2 and b=x. Your formula already has the '-' in it. Just use the formula and stop trying to double think it.
keishaap said:But the formula also has pi/2 + x there's 2 A's and 2 B's
Dick said:Use the formula SEPARATELY for each one. You can choose them differently for cos(pi/2-x) and cos(pi/2+x). Finish cos(pi/2-x) first, then worry about the other one.