Question

Find the exact value of 2sin135sin75? Would appreciate any help!

Answer 1

Ok, the answer is apparetnyl \[(1 + \sqrt{3})/2\], but I keep getting sqrt(6)/2?? Please help me.

Answer 2

Here is my work:

\[2(\sqrt{2}/2)\sin75°\]
\[2(\sqrt{2}/2)(\sqrt{3}/2)\] = \[\sqrt{6}/2\]

But the answer is supposed to be 1 + sqrt(3) / 2..
What am I doing wrong?

Answer 3

Ok lemme take a look But ya better Fan+Medal+Testimonial deal?

Answer 4

Sure! Thank you @Mimi_x3

Answer 5

I also got \[2(\sqrt{2}/2)(\sqrt{1}/2) \] but that doesn't get me the right answer.

Answer 6

Hey I am going to eat dinner but in the mean time maybe @dan815 Can help you. Otherwise ill be back in 20 minutes

Answer 7

Thank you! :)

Answer 8

sin(75deg) is not root3/2

Answer 9

@dan815 - I'm aware, but I just tried doing all I could and trying all possibilities. I converted sin75 into sin150/2 which got me root3/2 :(

Answer 10

it went from root(1-cos150/2) = root3/2 but It's wrong. I just don't know what to do since product - to - sum includes sin + sin but this is sin*sin so I'm lost!

Answer 11

its not sin*75

Answer 12

its sin of 75

Answer 13

sin is a big function that 75 is put into

Answer 14

Sin(75) + sin(75) is not equal to sin(150)

Answer 15

do you half angle formula or sin addition formula

Answer 16

sin(a+b)=?
or sin(2a)=?

Answer 17

I tried sin(theta/2) and that's how I got 150 since I didn't know sin of 75.

Answer 18

But I think I got the answer!! :)
I did 2*1/2(cos(135-75) - cos(135+75). Which equals 1(cos60 - 210) = 1(1/2 + root3/2) = (1 + root3)/2!! I got it! :D

Answer 19

Thanks for the help guys. I guess I was just stressing out and couldn't think straight. :)

Answer 20

ok good =] glad i cud help