Question

use the product to sum formula to write the product as a sum or difference 10 cos 75° cos 15°

Answer 1

use the identity :
2 cosAcosB = cos(A+B) + cos(A-B)

Answer 2

thanks! @RadEn

Answer 3

yw
did u get it ?

Answer 4

I did

Answer 5

that's cool :)

Answer 6

so, what ur answer --"

Answer 7

well I think I got it. isn't is Cos(75+15) + Cos(75-15) which is Cos (90) + Cos (60)

Answer 8

then, final answer is ...

Answer 9

Cos (90) =0 and Cos (60) = 1/2 so 0 +1/2 = 1/2

Answer 10

good,
but still incorrect, hihik :P

Answer 11

What am I doing wrong? :O

Answer 12

the final answer should be 5/2 :)

Answer 13

5cos(75 + 15) + 5 cos(75 - 15)

the terms 5sin75sin15 -5sin75sin15 = 0

Answer 14

hmmmm. i'm still not getting that

Answer 15

10 cos 75° cos 15°
= 5 (2 cos 75° cos 15°)
= 5 (you have already got this above)
= 5 (1/2)
= 5/2

hehe :)

Answer 16

hahaha thanks, you genius!

Answer 17

you're welcome ;)

Answer 18

just wondering are you a teacher? lol

Answer 19

jk. you're a junior. .