Pyramid 3D angles and lengths

[Kevinklb]

I calculated OA to be 16.4m using a2+b2=c2

Then angle I got was 59.22 degrees using cosine rule.
Can anyone tell me if I’m right?

 

[Otis]

I calculated OA to be 16.4m using a2+b2=c2

Hi Kevin. We type the caret symbol ^ to show exponents.

I get a different length for OA.

Please show your work using:
a^2 + b^2 = c^2



[imath]\;[/imath]

 

[Kevinklb]

Hi Kevin. We type the caret symbol ^ to show exponents.

I get a different length for OA.

Please show your work using:
a^2 + b^2 = c^2



[imath]\;[/imath]

 

[Kevinklb]

I was sure I was wrong here so not surprised you don’t agree

 

[Otis]

Thank you for identifying your triangle.

The length of DO is not given.

If we label the point at the center of the pyramid's base E, then the given, perpendicular height is EO.

In other words, you'll need to use the Pythagorean Theorem twice.



[imath]\;[/imath]

 

[Kevinklb]

Hi Otis thanks, see for the angle of OAC. I worked it out to be 59.2 degrees. Not sure that right tho as I used AC length as 16.7m? Would you give me mark for workings out being righg bug answer wrong?

 

[Otis]

Would you give me mark for [work] being [correct]

Hi Kevin. I don't recognize any correct work, on your second (expanded) image, except length 14.3 that you labeled for AD. Your lengths for AC, AO, CO, DO are not correct. You posted that you'd used the Law of Cosines, but I don't see it. I see an isolated inverse-sine expression (containing an improper equals sign).

It's hard to follow your work; it looks like scrap paper with partial statements. Both of your answers are wrong.

I'm not sure why you reposted an image that you'd already been told is incorrect. Are you interested in help to redo this exercise correctly, or are you posting just to inquire about people's grading opinions? I can help you with reworking the exercise, but I have no opinion regarding marks.

?

[imath]\;[/imath]

 

[Kevinklb]

Thanks for your opinion! Completely panicked during assessment and what a mess I made of it haha!! I didn’t realise I posted twice sorry.