赞 herrickfei 幼苗
共回答了21个问题采纳率：95.2% 举报
sin10°×sin50°×sin70°
= sin10°×sin50°×sin70°× cos10°/cos10°
= sin10°× cos10°×sin50°×sin70°/cos10°
= (1/2) × sin20°× sin50°× sin70°/cos10°
= (1/2) × sin20°× sin50°× cos20°/cos10°
= (1/4) × sin40°× sin50°/cos10°
= (1/4) × sin40°× cos40°/cos10°
= (1/8) × sin80°/cos10°
= (1/8) × sin80°/sin80°
= 1/8
【又
sin10°×sin50°×sin70°
=sin10°cos10°×cos20°×cos40°/cos10°
=.
= sin10°×sin50°×sin70°× cos10°/cos10°
= sin10°× cos10°×sin50°×sin70°/cos10°
= (1/2) × sin20°× sin50°× sin70°/cos10°
= (1/2) × sin20°× sin50°× cos20°/cos10°
= (1/4) × sin40°× sin50°/cos10°
= (1/4) × sin40°× cos40°/cos10°
= (1/8) × sin80°/cos10°
= (1/8) × sin80°/sin80°
= 1/8
【又
sin10°×sin50°×sin70°
=sin10°cos10°×cos20°×cos40°/cos10°
=.
1年前 追问
1
sin10°×sin50°×sin70°
=sin10°cos10°×cos20°×cos40°/cos10°
=1/2 sin20°×cos20°×cos40°/cos10°
=1/4 sin40°×cos40°/cos10°
=1/8 sin80°/cos10°
=1/8
=sin10°cos10°×cos20°×cos40°/cos10°
=1/2 sin20°×cos20°×cos40°/cos10°
=1/4 sin40°×cos40°/cos10°
=1/8 sin80°/cos10°
=1/8
可能相似的问题
-
1年前1个回答
-
1年前1个回答
-
若sin20°cos50°=a,则sin50°sin70°等于
1年前2个回答
-
1年前1个回答
-
1年前1个回答
-
1年前3个回答
-
1年前1个回答
-
sin20°sin10°-cos10°sin70°等于多少?
1年前1个回答
-
1年前1个回答
-
1年前1个回答
-
1年前1个回答
-
1年前2个回答
你能帮帮他们吗