Answer:
Hi myself Shrushtee.
Step-by-step explanation:
Your answer is
• c 15
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Step 1: Convert
, which is in radians into degrees. To convert it multiply by 

900/12
75
Step 2: 75 degrees isn't on the unit circle but 45 degrees and 30 degrees is. Since 45 + 30 = 75 you can use the cosine of 45 and 30 to find the exact value
cos45 = 
cos30 =
Step 3: Add the cos45 and cos30 to get cos5pi/12

Hope this helped!
Answer:
0.4
Step-by-step explanation:
4÷10
6.2 x 10^-3
Because when you add them together you get .0062 so you don't want anymore than one number to the left of decimal when in scientific notation therefore its 6.2 so you wanna move the decimal three spaces to the left to get .0062 therefore its 6.2x10^-3