the answer is D 6 8 10 is a scalene triangle
Answer:
The correct options are 1, 3 and 4.
Step-by-step explanation:
We need to find the expressions whose simplified form is a rational number.
Rational number: If a number is defined in the form of p/q where p and q are integers and q≠0, then it is called a rational number.
For example: 0,2, 4.3 etc.
Irrational number: If a number can not defined in the form of p/q, where p and q are integers and q≠0, then it is called an irrational number.
First expression is

12 is a rational number.
Second expression is

is an irrational number.
Third expression is

21 is a rational number.
Fourth expression is

5 is a rational number.
Therefore, the correct options are 1, 3 and 4.
If arctan 4/3 = the tangent of that angle will be 4/3 , opposite 4 over adjacent 3
Now, you only have to take the sin of that angle it's opposite 4 over hypotenuse 5.
You will get that the answer is 4/5
hope this helps
Number of combinations = (6x5) ÷ 2 = 15
Answer:There are 15 combinations