The answer they gave you for the first one is not correct.
Here is the right way:
sin 165
= sin(120+45)
= sin120cos45 + cos120sin45
= sin60sin45 + (-cos60sin45)
= (√3/2)(√2/2) - (1/2)(√2/2)
= (√6 - √2)/4
(my answer checked with calculator)
1)Find the exact value of sin 165 degrees.
Answer: (sqrt6 + sqrt2)/4
2) Simplify: (4m/5n^2)- (n/2m)
Answer: (8m^2-5n^3)/10n^2m
Thanks
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