Question #27d6b

1 Answer
Somebody N.
Nov 29, 2017

See below.

Explanation:

Using identities:

#color(red)(sin(A-B)=sinAcosB-cosAsinB)#

#color(red)(sin(A+B)=sinAcosB+cosAsinB)#

#sin(180-c)=sin(180)cos(c)-cos(180)sin(c)#

#sin(180-c)=(0)cos(c)-(-1)sin(c)#

#sin(180-c)=sin(c)#
..................................................................................................................................

#sin(180+c)=sin(180)cos(c)+cos(180)sin(c)#

#sin(180+c)=(0)cos(c)+(-1)sin(c)#

#sin(180+c)=-sin(c)#

As to remembering. I think you just remember them when you keep using them.

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