on3winyoureyes
New member
- Joined
- Jan 20, 2015
- Messages
- 20
verify it's an identity:
cos(90°+x) = -sinx
My work
cos(90°+x) = -sinx
=cos90°+cosx
=cos90° is 0 so 0+cosx
(cos90)(cosx)-(sin90)(sinx)
=0-sinx
-sinx=-sinx
cos(90°+x) = -sinx
My work
cos(90°+x) = -sinx
=cos90°+cosx
=cos90° is 0 so 0+cosx
(cos90)(cosx)-(sin90)(sinx)
=0-sinx
-sinx=-sinx
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