Question

Find the exact value of the expression cos75 degrees sin15 degrees+sin75 degrees cos 15degrees.

Answer 1

use the identity

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

Answer 2

what identity is

Answer 3

that exactly>?

Answer 4

if we take a to be 75, and b to be 15

then sin (a + b) = sin (75 + 15) = sin 90

and what is the value of sin 90?

Answer 5

soorrhy but i dnt understand this is there an

Answer 6

another way?

Answer 7

i dont think so
look at the formula again and read it from left to right

Answer 8

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

so

sin 75 cos 15 + cos 75 sin 15 = sin ( 75 + 15) (replacing a by 75 and b by 15)

Answer 9

and sin 90 = 1
so the exact value is 1