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.
Sum and difference identities equations are mathematical equations that express the relationship between the sum or difference of two angles or trigonometric functions. These equations are used to simplify trigonometric expressions and solve problems involving multiple angles.
Sum and difference identities equations can be proved using the fundamental trigonometric identities, such as the Pythagorean identities and the double angle identities. These identities can be used to manipulate the equations and show that both sides are equal.
Examples of sum and difference identities equations include: sin(A + B) = sinAcosB + cosAsinB, cos(A - B) = cosAcosB + sinAsinB, and tan(A + B) = (tanA + tanB) / (1 - tanAtanB). These equations can be used to find the value of trigonometric functions for multiple angles.
Sum and difference identities equations are used in various fields such as engineering, physics, and navigation. They are used to calculate the angles and distances between objects, as well as to analyze and predict the behavior of waves, sound, and light.
A helpful way to remember sum and difference identities equations is by using the acronym "SOHCAHTOA", which stands for sine equals opposite over hypotenuse, cosine equals adjacent over hypotenuse, and tangent equals opposite over adjacent. This can serve as a guide to help you recall and apply the equations when needed.