If α + β = 120 °, then the minimum value of y = Sin & # 178; α + Sin & # 178; β is

If α + β = 120 °, then the minimum value of y = Sin & # 178; α + Sin & # 178; β is
1/2
solution
Let α = 60 ° + M
β=60°-m
M is any degree
After the power is reduced by the double angle formula, it is expanded by the cosine sum difference formula
y=sin²α+sin²β
=1+1/2cos2m
therefore
The minimum is 1 / 2

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