SIN10°SIN30°SIN50°SIN70°SIN90°=(1/2)*SIN10°SIN50°SIN70°
=(1/4)*2COS10°SIN10°SIN50°SIN70°/COS10°
=(1/4)*SIN20°SIN50°SIN70°/COS10°
=(1/8)*2COS20°SIN20°SIN50°SIN70°/(COS10°COS20°)
=(1/8)*SIN40°SIN50°SIN70°/(COS10°COS20°)
=(1/16)*2COS40°SIN40°SIN50°SIN70°/(COS10°COS20°COS40°)
=(1/16)*SIN80°SIN50°SIN70°/(COS10°COS20°COS40°)
=1/16