Question

数学题，怎么写啊，写纸上

Answer 1

写纸上你就为难我了

Answer 2

f(x) = (√3/2)(1+cos2x) + (1/2)sin2x = √3/2 + sin(2x+π/3)
(1) 最小正周期 T = π。
单调递减区间 , 2kπ+π/2 < 2x+π/3 < 2kπ+3π/2
2kπ+π/6 < 2x < 2kπ+7π/6, kπ+π/12 < x < kπ+7π/12.
(2) f(A/2-π/6) = √3/2 + sinA = √3, sinA = √3/2, A = π/3 或 A = 2π/3.
S = (1/2)bcsinA = (√3/2)b =2√3, b = 4,
a^2 = b^2 + c^2 -2bccosA = 16 + 4 - 16cosA,
A = π/3 时， a^2 = 12, a = 2√3;
A = 2π/3 时， a^2 = 28, a = 2√7 。