Hi, there--



The Problem:

Use an identity to easily find: sin(100°)cos(10°)-cos(100°)sin(10°)



A Solution:

I would use the identity for the sine of the difference of two angles.

sin(u-v) = sin(u)cos(v)-cos(u)sin(v)

.

In your problem, 

u = 100°

v = 10°



Then,

sin(100°)cos(10°)-cos(100°)sin(10°) = sin(100°-10°) = sin(90°) = 1



Feel free to email if you questions about this solution.



Ms.Figgy

math.in.the.vortex@gmail.com 

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