1.y=lg(sinx+cosx)的定义域为?2.y=cos(x-π/6)(x∈[π/6,2π/3])的最小值是?

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1.y=lg(sinx+cosx)的定义域为?2.y=cos(x-π/6)(x∈[π/6,2π/3])的最小值是?1.y=lg(sinx+cosx)的定义域为?2.y=cos(x-π/6)(x∈[π/

1.y=lg(sinx+cosx)的定义域为?2.y=cos(x-π/6)(x∈[π/6,2π/3])的最小值是?
1.y=lg(sinx+cosx)的定义域为?
2.y=cos(x-π/6)(x∈[π/6,2π/3])的最小值是?

1.y=lg(sinx+cosx)的定义域为?2.y=cos(x-π/6)(x∈[π/6,2π/3])的最小值是?
1.真数大于0,sinx+cosx=sin(x+π/4)大于0,用单位圆想,就是
0+2kπ小于x+π/4小于π+2kπ
所以定义域(-π/4+2kπ,3π/4+2kπ),(k∈Z)
2.因为x∈[π/6,2π/3],所以x-π/6∈[π/3,5π/6],用单位圆想,
fmin=f(5π/6)=(负二分之根号3)