How do I do this
Need details solution to follow up
prove that cos(a)+cos(a+b)+cos(a+2b)+....+cos(a+(n-1)b)={cos(a+((n-1)/2)bsin(nB/2)}/½sinb
for all N£N
Hmmm. It's not even true for n=2, so I think something's wrong.
How is it not true can you explain?
geez - plug in n=2 and the equation generated is not true.
This is part of an IMO question which I can't solve
A question cannot be false. Apparently the identity they proposed is not true.
Take a look at what happens when
n=1: cos(a) = 2cos(a - b/2)sin(b/2)/sin(b)
n=2: cos(a) + cos(a+b) = 2cos(a + b/2)sin(b)/sin(b)
clearly neither of those is an identity.
You can find answers to past IMO's online. They really are quite difficult. Maybe you should start with the MAA's AHSME, which is the gateway to the IMO. It's kind of the next step up from the SAT math area exams. I got 800 on each of those, and felt pretty competent, but blew it royally on the AHSME, even though I was top in my high school for three years running.
To tell you the truth, I have only tried a few IMO problems. They really require some sophistication and out-of-the-box thinking. If you finally get past the IMO, you can move on to the Putnam exam, given to college students. Two sets of six questions, each three hours. I got 11 out of 120 points, which is about average!
Wow.......thanks sir obleck
You're the best thanks for the info
Can you give me a link to download
MAA's AHSME book??