Question

cos75 = (√6+√2)/4

... correct?

Answer 1

false

Answer 2

cos75 = cos45+30 = cos45cos30 - sin45sin30.....

Answer 3

(sqrt(3)-1)/(2 sqrt(2))

Answer 4

\[(\sqrt{3}-1)\div(2\sqrt{2})\]

Answer 5

? i've got cos45 = √ 2/2 , cos30=√ 3/2, sin45 = √ 2/2, sin30=1/2

Answer 6

diogo has it

Answer 7

if you rationalize denminator you get
\[\frac{\sqrt{6}-\sqrt{2}}{4}\]

Answer 8

.... confused, √ 2/2 * √ 3/2 = √ 6/4 , and 1/2 * √ 2/2 = √ 2/4, so ...... AH, the symbol is minus, but the numbers are correct, right?

Answer 9

so my post should read:

"cos75 = (√6-√2)/4 .... correct?"

Answer 10

yes

Answer 11

cos75=cos(45+30)
=cos45cos30-sin45sin30
=(1/2^.5)(3^.5/2)-(1/2^.5)1/2
(3^.5-1)/2*2^.5
false