Answer:
[tex]cos(30\°) = cos(45\°-15\°)[/tex]
Step-by-step explanation:
To solve this problem you must know the formula of subtraction of angles for the function cosx.
The formula is:
[tex]cos(h-d) = cos(h)cos(d) + sin(h)sin(d)[/tex]
We can write 30° as: 45° - 15°
Then:
[tex]cos(30\°) = cos(45\°-15\°)[/tex]
Using the formula for subtraction of angles we have:
[tex]cos(45\°-15\°) = cos(45\°)cos(15\°) + sin(45\°)sin(15\°)[/tex]
Notice that we have achieved the expression shown in the statement
Finally:
[tex]cos(30\°) = cos(45\°-15\°)[/tex]
Answer:
square root 3/2
Step-by-step explanation:
on usatestprep and the unit circle
