Since both α and β are in the first quadrant, we know each of cos(α), sin(α), cos(β), and sin(β) are positive. So when we invoke the Pythagorean identity,
sin²(x) + cos²(x) = 1
we always take the positive square root when solving for either sin(x) or cos(x).
Given that cos(α) = √11/7 and sin(β) = √11/4, we find
sin(α) = √(1 - cos²(α)) = √38/7
cos(β) = √(1 - sin²(β)) = √5/4
Now, recall the sum identity for cosine,
cos(x + y) = cos(x) cos(y) - sin(x) sin(y)
It follows that
cos(α + β) = √11/7 × √5/4 - √38/7 × √11/4 = (√55 - √418)/28
Answer:
34% = 272 students
100% = 272/34%
= 800 students
Step-by-step explanation:
to check whether the answer is correct
= 34% × 800
= 272 students
A= 20x25 so the area is 500
To find the perimeter you have to add both the width and length x2 so it’s 20+25 =45
45x2=90
20% off of $15 is 12.00
And 5% of 12.00 is .60
So your answer is $12.60
If this helps mark as brainliest pls
Step-by-step explanation:
for 1 book=480
for 4 books= 480×4
=1920
