✔ 最佳答案
令s=sin(t), c=cos(t), 則原式為:2√(1-c^2)=15(4c^3-3c)兩邊平方得到6次方程式:4(1-c^2)=225(16c^6-24c^4+9c^2)0=3600c^6-5400c^4+2029c^2-4=3600x^3-5400x^2+2029x-4.....x=c^2透過電腦輔助計算:x1=0.001981854 => c1=+-0.044518x2=0.7297 => c2=+-0.85423x3=0.7683 => c3=+-0.87653所以解答為:t1=acos(+-c1)=87.45°,92.55°t2=acos(+-c2)=31.325°,148.675°t3=acos(+-c3)=28.77°,151.227°