Question

Trigonometry: Power-reducing and half-angle formulas! http://prntscr.com/45ak6v

Answer 1

Da herro, @mathstudent55

Answer 2

One more: http://prntscr.com/45aoan

Answer 3

@mathstudent55 Herro?

Answer 4

@ganeshie8

Answer 5

Bump isn't working for me so I'm tagging anyone who can help...

Answer 6

do you recall the formula for say: cos(a+b) ??

Answer 7

I'm on vacation for a week and have no formula sheet (or equivalencies for that matter).

Answer 8

it can be determined from a drawing as well

Answer 9

Okay, I'm following

Answer 10

cos(a+b) is determined by subtracting sin(a)sin(b) from cos(a)cos(b)

cos(a+b) = cos(a)cos(b) - sin(a)sin(b)

now, when a=b, lets say they both equal x

cos(x+x) = cos(x)cos(x) - sin(x)sin(x)

cos(2x) = cos^2(x) - sin^2(x)