Given:
To find:
The exact value of cos 15°.
Solution:
Using half-angle identity:
Using the trigonometric identity:
Let us first solve the fraction in the numerator.
Using fraction rule:
Apply radical rule:
Using :
Answer
Find out the how long will it take the submarine to descend to the ocean floor
To proof
Formula
where d = distance traveled (or descended),
r = rate of travel , t = time
As given
A submarine descends at a rate of 2.6 kilometers per hour. If the ocean floor is 6.24 kilometers below sea level .
put all the values in the above formula
t = 2.4 hour
it take 2.4 hours the submarine to descend to the ocean floor .
Hence proved