Question

Find an exact value.

cos 75°

Answer 1

In radian? Or degree mode?

Answer 2

@SGREBORN for example, like -sqrt(6)+sqrt(2)

Answer 3

Is this topic on Imaginary numbers?

Answer 4

first, setting 75 = 30+45
then use the formula :
cos(A+B) = cosAcosB - sinAsinB
here, given A=30 and B=45

Answer 5

@RadEn so i got cos30cos45-sin30sin45
how do i simplify this?

Answer 6

do u know what the values of cos30, cos 45, sin 30, and sin45 degrees ?
they all the special degrees, u have to memorize it :)

Answer 7

@RadEn ahh is this unit circle? I forgot:(

Answer 8

it is trigonometry

Answer 9

well, if u forgot i will refresh ur memories :)
cos30 = 1/2 * sqrt(3)
cos45 = 1/2 * sqrt(2)
sin30 = 1/2
sin45 = 1/2 * sqrt(2)
now, apply of them to formula above

Answer 10

@RadEn
so it will be {sqrt(6) - sqrt(2)}/4?

Answer 11

yes, u are right

Answer 12

@RadEn Thankyou!