Sin10°cos60°sin50°cos20°sin90°不查表求值
2个回答

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