Answer: cos(Θ) = (√15) / 4
Explanation:
The question states:
1) sin(Θ) = 1/4
2) 0 < Θ < π / 2
3) find cos(Θ)
This is how you solve it.
1) Use the fundamental identity (in this part I use α instead of Θ, just for facility of wirting the symbols, but they mean the same for the case).

2) From which you can find:

3) Replace sin(α) with 1/4
=>

=>

4) Given that the angle is in the first quadrant, you know that cosine is positive and the final answer is:
cos(Θ) =

.
And that is the answer.
Answer
None of the above
Step-by-step explanation:
Answer:
x = ± 
Step-by-step explanation:
Given
2x² - 9 = 11 ( add 9 to both sides )
2x² = 20 ( divide both sides by 2 )
x² = 10 ( take the square root of both sides )
x = ±
← exact solutions
jeez that looks really hard
Step-by-step explanation: