Recall the sum identity for cosine:
cos(a + b) = cos(a) cos(b) - sin(a) sin(b)
so that
cos(a + b) = 12/13 cos(a) - 8/17 sin(b)
Since both a and b terminate in the first quadrant, we know that both cos(a) and sin(b) are positive. Then using the Pythagorean identity,
cos²(a) + sin²(a) = 1 ⇒ cos(a) = √(1 - sin²(a)) = 15/17
cos²(b) + sin²(b) = 1 ⇒ sin(b) = √(1 - cos²(b)) = 5/13
Then
cos(a + b) = 12/13 • 15/17 - 8/17 • 5/13 = 140/221
Answer:
162.4 in²
Step-by-step explanation:
LETS GET INTOOOOEEETTT
Let's start with what we know:
Area of regular octagon = 1/2 x perimeter x apothem
We know the apothem, so all that we need to find to fill in the above equation is the perimeter:
perimeter = 8 x 5.8 = 46.4in
Now we can fill in our original equation and solve:
Area of regular octagon = 1/2 x perimeter x apothem
Formula = n (s/2)² divided by tan( π /n)
= 8 (5.8/2)² divided by tan ( π /8)
= 162.4283 in²
ORRR when rounded to the nearest tenth,
=162.4 in²
Answer:
X= -4
Step-by-step explanation:
Answer:
The Answer would be C, i think
Step-by-step explanation:
