计算cot70°tan(-50°)-1tan20°-tan50°的值是 _____爱下问搜题

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问题填空题

计算

cot70°tan(-50°)-1

tan20°-tan50°

的值是 ______．

答案

cot70°tan(-50°)-1

tan20°-tan50°

=

tan20°tan(-50°)-1

tan20°-tan50°

=

tan20°tan50°+1

tan50°-tan20°

=

1

tan30°

=

3

故答案为：

3

选择题

He went there as a volunteer on a ________ program.

A．two-year

B．two-years

C．two-year’s

D．two years

填空题

为防止使铸件产生缩孔和缩松，应使铸件实现（）。