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2 years ago

Evaluate cos 7pi/8 without a calculator

Mathematics

2 answers:

NISA [10]2 years ago

8 0

Hey there!

7π/8

= 7(3.141593)/8

= 2.748894

3.141593 ≈ 3.14

= 7(3.14)/8

= 21.98/8

= 21.98 ÷ 8

= 2.7475

Answer: 2.748894 WHICH IS APPROXIMATELY 2.7475

Good luck on your assignment and enjoy your day!

~Amphitrite1040:)

Olin [163]2 years ago

4 0

Answer: Long answer- 2.748893572

Short answer- 2.7475

Step-by-step explanation:

Long Answer:

7(3.141592654)/8

Step 1: 7 x 3.141592654= 21.99114858

Step 2: 21.99114858/8= 2.748893572

Short Answer: 7(3.14)/8

Step 1: 7x3.14= 21.98

Step 2: 21.98/8= 2.7475

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Answer:

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3 years ago

An airplane travels 6111 kilometers against the wind in 9 hours and 7911 kilometers with the wind in the same amount of time. Wh

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Answer:

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Step-by-step explanation:

Assume that $x\; {\rm km \cdot h^{-1}}$ is the speed of the plane in still air, and that $y\; {\rm km \cdot h^{-1}}$ is the speed of the wind.

When the plane is travelling against wind, the ground speed of this plane (speed of the plane relative to the ground) would be $(x - y)\; {\rm km \cdot h^{-1}}$ .
When this plane is travelling in the same direction as the wind, the ground speed of this plane would be $(x + y)\; {\rm km \cdot h^{-1}}$ .

The question states that when going against the wind ( $v = (x - y)\; {\rm km \cdot h^{-1}}$ ,) the plane travels $6111\; {\rm km}$ in $9\; {\rm h}$ . Hence, $9\, (x - y) = 6111$ .

Similarly, since the plane travels $7911\; {\rm km}$ in $9\; {\rm h}$ when travelling in the same direction as the wind ( $v = (x + y)\; {\rm km \cdot h^{-1}}$ ,) $9\, (x + y) = 7911$ .

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