Answer:
0.38268343
Step-by-step explanation:
cos(
67.5
)
Rewrite
67.5
as an angle where the values of the six trigonometric functions are known divided by 2
.
cos
(
135\
2)
Apply the cosine half-angle identity.
±
√
1
+
cos
(
135
)
2
Change the
±
to
+
because cosine is positive in the first quadrant.
√
1
+
cos
(
135
)
2
Simplify
√
1
+
cos
(
135
)
2
√
2
−
√
2
2
The result can be shown in multiple forms.
Exact Form:
√
2
−
√
2
2
Decimal Form:
0.38268343
…
(a) You can plant 7 1/4 acres per pound of seed
(b) Isabel takes 7 minutes to run a mile
Try this solution:
Answer: 6 & 4.5 (m-per-h)
Step-by-step explanation:
- The basic formula used in this task is S=V*t, where S - distance, V - speed, t - time.
- the downstream speed is: V+Vc, where V - the speed of the boat in still water, Vc - the speed of the current.
- the upstream speed is: V-Vc.
- according to the described above the distance for downstream is S1=(V+Vc)*t1, where t1=10; the distance for upstream is S2=(V-Vc)*t2, where t2=70.
- for whole travel down- and upstream: S=S1+S2.
- Using these it is possible to make up the system of the equations:

V - the speed of the boat in still water - 6 miles per hour, Vc - the speed of the current - 4.5 miles per hour. All the details for the system of the equations are in the attachment.
Answer:
1 3/8
Step-by-step explanation: