#1**+1 **

First off we want to note that sin(x) = cos(90-x)

Then if you plug in 17 for x you get:

sin(17-5) = cos(4*17+10)

which is

**sin(12) = cos(78)**

now lets see if this equation is equal by using sin(x) = cos(90-x)

so x would be 12 in this case.

so

sin(12) = cos(90-12)

sin(12) = cos(78)

this is the same answer that we got before (in bold)

so the statement is true

Guest Mar 17, 2019