WAVE SPEED: 2. Speed = wavelength x frequency. What is the speed of a wave with a wavelength of 73m and a frequency
of 15.25Hz?

the value of x is 9 ⇒ answer b

step-by-step explanation:

* we can solve this problem using cosine and sine rule

- in δ abc

∵ ab = 36 , bc = 28 , ac = 16

- lets find the measure of angle b using the cosine rule

∵ cos b = [ab² + bc² - ac²]/2(ab)(bc)

∴ cos b = [36² + 28² - 16²]/2(36)(28)

∴ cos b = 19/21

∴ m∠b = cos^-1(19/21) ≅ 25°

- lets find the measure of angle a using the sine rule

∵ sina/bc = sinb/ac = sinc/ab

∴ sina/28 = sin25°/16 ⇒ by using cross multiplication

∴ sina = 28 × sin25°/16

∴ sina = 0.7396

∴ m∠a = sin^-1(0.7396) ≅ 48°

- from the figure m∠abd = m∠dbc

∵ m∠abc = 25°

∴ m∠abd = 25°/2 = 12.5°

- in δabd

∵ m∠a = 48° , m∠abd = 12.5°

∵ the sum of the measures of the interior angles of any δ is 180°

∴ m∠adb = 180° - (48° + 12.5°) = 119.5°

∵ ab = 36

∵ ad = x

- use the sine rule to find x

∵ sin∠adb/ab = sin∠abd/x

∴ sin119.5°/36 = sin12.5°/x ⇒ by using cross multiplication

∴ x = 36 × sin12.5°/sin119.5° = 8.95 ≅ 9

* the value of x is 9

to find the unit price of an object, you divide the price by object. you are trying to find out how much an object cost per unit.

for instance, lets say you have 50lb of ice cream(object) that cost 8.00 dollars(price). to find the unit cost, we take the 8.00 and divide it by 50, which will give us .16 cents per pound. we can check this by multiplying .16 by 50 = 8.00

so

object = e2

price = d2

unit price = c2

formula for c2:

=d2 / e2

so in my example about ice cream, we would have the following.

e2 = 50

d2 = 8.00

c2 formula:

=d2 / e2

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