Question

The picture shows a portion of a river dam.

What is the height, in meters, of the river dam?

I keep coming up with 287 using cos 40 degrees
H = 220/cos 40

Answer 1

take cosine of 40 degrees

Answer 2

cos 40 = height / 220

Answer 3

Yeah that's what I did, sorry.

Answer 4

yes because we are taking cosine of 40 or you can take sine of 50 = height of triangle / 220

Answer 5

then multiply both sides by height then divide both by cos 40

Answer 6

well if use of calculator is permitted find cos 40 =0.777 approx
your answer is 220*0.777

Answer 7

yeah I got .766

Answer 8

let me know if you still do not have the answer

Answer 9

Then I got 287 but that's larger than they hypotenuse, that's where I was stuck.

Answer 10

it shoud be about 168

Answer 11

Oh what the heck... let me re-work it on my calc.

Answer 12

Yeah I get the same. I have to idea what I'm doing wrong!

Answer 13

do you have a windows pc ?

Answer 14

yeah I'm using the calculator on my computer

Answer 15

ok, press start, access the calculator in scientific mode, then press 40 and click "cos" function
it will give ya a value of say .768, then multiply that answer by 220

Answer 16

Oh I was dividing 220 by .766!

Answer 17

Isn't it 220/cos 40 then 220/.766 then obviously I got 287...

Answer 18

cos 40= height / 220, solving for height ; we get height = 220* cos 40

Answer 19

I don't see how you get from dividing both sides by cos 40 to multiplying it by 220

Answer 20

well we are solving for height so we need multiply both side by 220 to eliminate 220 from right side of the equation

Answer 21

but in any other trigonometric situation you wouldn't do that?

Answer 22

well i can give you a second alternative,
sin 50= height /220,
to solve for height we would need to get 220 on the left side of equation,
height = 220*sin 50
so essentially you have done the same thing here too : )

Answer 23

You'd do exactly what I did to solve this, wouldn't you?
cos 40 = h/220
h * cos 40 = h * h/ 220
then divide both sides by cos 40
h = 220/cos 40

This so far is wrong?

Answer 24

step 1 is correct
well you made a minor mistake in step 2
instead of writing h*cos40 = h*h /220 we need to have
220* cos 40 = h*220 / 220, thus doing you moved 220 from denominator of right side to the numerator of left side,

simply, cross multiply

Answer 25

Oh okay, I'm following my lessons rules and they do it differently that's why I was confused.

Answer 26

featheres aint pellet and they dont know nunthin