计算number的余弦函数，输入为弧度值。
命令格式
double|decimal cos(<number>)参数说明
number：必填。DOUBLE或DECIMAL类型。输入为STRING、BIGINT类型时，会隐式转换为DOUBLE类型后参与运算。
返回值说明
返回DOUBLE或DECIMAL类型。返回规则如下：
number为DOUBLE、DECIMAL类型时会返回相应的类型。
number为STRING、BIGINT类型时，返回DOUBLE类型。
number值为NULL时，返回NULL。
示例数据
为便于理解各函数的使用方法，本文为您提供源数据，基于源数据提供函数相关示例。创建表mf_math_fun_t，并添加数据，命令示例如下。
create table if not exists mf_math_fun_t(
int_data int,
bigint_data bigint,
double_data double,
decimal_data decimal,
float_data float,
string_data string
);
insert into mf_math_fun_t values
(null, -10, 0.525, 0.525BD, cast(0.525 as float), '10'),
(-20, null, -0.1, -0.1BD, cast(-0.1 as float), '-10'),
(0, -1, null, 20.45BD, cast(-1 as float), '30'),
(-40, 4, 0.89, null, cast(0.89 as float), '-30'),
(5, -50, -1, -1BD, null, '50'),
(-60, 6, 1.5, 1.5BD, cast(1.5 as float), '-50'),
(-1, -70, -7.5, -7.5BD, cast(-7.5 as float),null ),
(-80, 1, -10.2, -10.2BD, cast(-10.2 as float), '-1' ),
(9, -90, 2.58, 2.58BD, cast(2.58 as float), '0'),
(-100, 10, -5.8, -5.8BD, cast(-5.8 as float), '-90');查询表mf_math_fun_t中的数据，命令示例如下：
select * from mf_math_fun_t;
--返回结果。
+------------+-------------+-------------+--------------+------------+-------------+
| int_data | bigint_data | double_data | decimal_data | float_data | string_data |
+------------+-------------+-------------+--------------+------------+-------------+
| NULL | -10 | 0.525 | 0.525 | 0.525 | 10 |
| -20 | NULL | -0.1 | -0.1 | -0.1 | -10 |
| 0 | -1 | NULL | 20.45 | -1.0 | 30 |
| -40 | 4 | 0.89 | NULL | 0.89 | -30 |
| 5 | -50 | -1.0 | -1 | NULL | 50 |
| -60 | 6 | 1.5 | 1.5 | 1.5 | -50 |
| -1 | -70 | -7.5 | -7.5 | -7.5 | NULL |
| -80 | 1 | -10.2 | -10.2 | -10.2 | -1 |
| 9 | -90 | 2.58 | 2.58 | 2.58 | 0 |
| -100 | 10 | -5.8 | -5.8 | -5.8 | -90 |
| NULL | -10 | 0.525 | 0.525 | 0.525 | 10 |
| -20 | NULL | -0.1 | -0.1 | -0.1 | -10 |
| 0 | -1 | NULL | 20.45 | -1.0 | 30 |
| -40 | 4 | 0.89 | NULL | 0.89 | -30 |
| 5 | -50 | -1.0 | -1 | NULL | 50 |
| -60 | 6 | 1.5 | 1.5 | 1.5 | -50 |
| -1 | -70 | -7.5 | -7.5 | -7.5 | NULL |
| -80 | 1 | -10.2 | -10.2 | -10.2 | -1 |
| 9 | -90 | 2.58 | 2.58 | 2.58 | 0 |
| -100 | 10 | -5.8 | -5.8 | -5.8 | -90 |
+------------+-------------+-------------+--------------+------------+-------------+使用示例：静态数据示例
--返回2.6794896585028633e-8。
select cos(3.1415926/2);
--返回-0.9999999999999986。
select cos(3.1415926);
--返回NULL。
select cos(null);使用示例：表数据示例
基于示例数据，计算余弦值，命令示例如下。
select cos(bigint_data) as bigint_new, cos(double_data) as double_new, cos(decimal_data) as decimal_new, cos(string_data) as string_new from mf_math_fun_t;返回结果如下。
+---------------------+--------------------+----------------------+---------------------+
| bigint_new | double_new | decimal_new | string_new |
+---------------------+--------------------+----------------------+---------------------+
| -0.8390715290764524 | 0.8653239416229412 | 0.8653239416229412 | -0.8390715290764524 |
| NULL | 0.9950041652780258 | 0.9950041652780258 | -0.8390715290764524 |
| 0.5403023058681398 | NULL | -0.02964340851507803 | 0.15425144988758405 |
| -0.6536436208636119 | 0.6294120265736969 | NULL | 0.15425144988758405 |
| 0.9649660284921133 | 0.5403023058681398 | 0.5403023058681398 | 0.9649660284921133 |
| 0.960170286650366 | 0.0707372016677029 | 0.0707372016677029 | 0.9649660284921133 |
| 0.6333192030862999 | 0.3466353178350258 | 0.3466353178350258 | NULL |
| 0.5403023058681398 | -0.7142656520272003| -0.7142656520272003 | 0.5403023058681398 |
| -0.4480736161291701 | -0.8464080412157756| -0.8464080412157756 | 1.0 |
| -0.8390715290764524 | 0.8855195169413189 | 0.8855195169413189 | -0.4480736161291701 |
+---------------------+--------------------+----------------------+---------------------+相关函数
COS函数属于数学函数，更多数据计算、数据转换的相关函数请参见数学函数。