应该是角度制下的角度值吧?!
cos36°+cos72°+cos108°+cos144°
=cos36°+cos72°+cos(180°-72°)+cos(180°-36°)
=cos36°+cos72°-cos72°-cos36°
=0
求cos36+cos72+cos108+cos144的值.写出计算过程.
应该是角度制下的角度值吧?!
cos36°+cos72°+cos108°+cos144°
=cos36°+cos72°+cos(180°-72°)+cos(180°-36°)
=cos36°+cos72°-cos72°-cos36°
=0