cos(a+π/6)=2/3 a+π/6范围为 π/6到2π/3 sin(a+π/6)=√5/3(是三分之根号五)
√3/2cosa-1/2sina=2/3 (1)
√3/2sina+1/2cosa=√5/3(2)
(1)x√3+(2)得2cosa=2√3+√5/3
cosa=(2√3+√5)/6
cos(a+π/6)=2/3 a+π/6范围为 π/6到2π/3 sin(a+π/6)=√5/3(是三分之根号五)
√3/2cosa-1/2sina=2/3 (1)
√3/2sina+1/2cosa=√5/3(2)
(1)x√3+(2)得2cosa=2√3+√5/3
cosa=(2√3+√5)/6