cos2x-sin²x-cos²x+2sinx cosx=0
cos2x-1+2sinx cosx=0
cos2x+2sinx cosx=1
cos2x+sin2x=1
(√2/2)(cos2x+sin2x)=√2/2
(√2/2)cos2x+(√2/2)sin2x=√2/2
sin(π/4)cos2x+cos(π/4)sin2x=√2/2
sin(2x+π/4)=√2/2
∵ 0≤x≤2π
∴ π/4 ≤ 2x+π/4 ≤ 17π/4
→ 2x+π/4 = π/4 或 3π/4 或 9π/4 或 11π/4 或 17π/4
x = 0 或 π/4 或 π 或 5π/4 或 2π
(是要把所有解加起來嗎?)
0 + π/4 + π + 5π/4 + 2π = 9π/2
→ p=2, q=9
→ p+q=11
感謝感謝