engineering derivations for lateral earth pressure coefficient on a retaining wall

my text book on soils engineering advises that the lateral earth pressure coefficient is determined by: (1-sin(x))/(1+sin(x)), however it also advises that by simple trigonometry this can also be written as tan^2(pi/4-(x)/2). how do you get from the first to equal the second using trigonometry?

How to play Pathfinder in a future Earth setting? [on hold]

I am putting together a homespun world for my PCs to play Pathfinder in. Rather than being based on high fantasy, it is set in a future Earth, post-calamity setting. It has been several thousand years since the calamity, and vestiges of the old world remain: Remnants of technology, for instance… Books in ancient languages containing forgotten knowledge… And, somehow, magic has entered the world.

I would like to play in this setting, and I would like to leverage all of the Pathfinder rules that I have access to – but I want to refactor them so that they make sense in this world. I want to concentrate on building the world, leveraging the Pathfinder rules I already have access to and have invested in, while minimizing the required effort to do so. Any advice?

Update Manager Issues regarding Google Earth

Any help regarding the following error would be greatly appreciated. I have tried some apt commands to clean it up but to no avail. I am running a Dell Latitude E6510 with LinuxM Mint 19. Thanks, in advance, for any assistance. John.

“An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: stable Release: The following signatures were invalid: EXPKEYSIG 1397BC53640DB551 Google Inc. (Linux Packages Signing Authority) Failed to fetch The following signatures were invalid: EXPKEYSIG 1397BC53640DB551 Google Inc. (Linux Packages Signing Authority) Some index files failed to download. They have been ignored, or old ones used instead.”

Why my Google earth exported KMZ file is not a XML file but a binary one?

According to wikipedia, kmz is a:

DescriptionKeyhole Markup Language is an XML notation for expressing geographic annotation and visualization within Internet-based, two-dimensional maps and three-dimensional Earth browsers. KML was developed for use with Google Earth, which was originally named Keyhole Earth Viewer.

However, the KMZ file got exported by Google Earth is not a XML one. It’s even not a XML file but a binary file.

How can I see the XML content?


Good Vs. Evil – Battle For Middle Earth – CodeWars

This is the code that I’m submitting for the “Good vs Evil” Kata on CodeWars:

function goodVsEvil(good, evil) {   good = good.split(' ');   evil = evil.split(' ');    //hobbits, men, elves, etc   let goodWorth = [1, 2, 3, 3, 4, 10];   //orcs, men, wargs, etc     let evilWorth = [1, 2, 2, 2, 3, 5, 10];    let goodArmyPoints = [];   //multiply goodWorth by type:   for (let i = 0; i < goodWorth.length; i++) {     goodArmyPoints.push(good[i] * goodWorth[i]);   }    goodArmyPoints = goodArmyPoints.reduce(function (sum, value) {     return sum + value;   });    let evilArmyPoints = [];   for (let j = 0; j < evilWorth.length; j++) {     evilArmyPoints.push(evil[j] * evilWorth[j]);   }    evilArmyPoints = evilArmyPoints.reduce(function (sum, value) {     return sum + value;   });    if (evilArmyPoints < goodArmyPoints) {     return "Battle Result: Good triumphs over Evil";   } else if (evilArmyPoints > goodArmyPoints) {     return "Battle Result: Evil eradicates all trace of Good";   } else {     return "Battle Result: No victor on this battle field";   }  } 

But I’m not sure what:

goodArmyPoints = goodArmyPoints.reduce(function (sum, value) {     return sum + value;   }); 

is doing exactly.

I see that reduce “executes a reducer function (which I’ve provided?) on each member of the array, resulting in a single output value”.

But can someone please walk me through what .reduce(function (sum, value) is doing, exactly? Where is this function coming from? What are sum and value?

I’m still learning JavaScript and this is new to me. Thanks.

Is the Earth visible from the Moon in Google Maps?

After a while of random searching and everyday checking, today (I believe) I finally found the Moon in Google Maps while looking at the Earth. Distance looks good and even the shadow matches with Earth’s. I also noticed that Google Maps recognize it as a valid object by pressing F5 observing the difference in load times of each component (celestial bodies vs. background).,41.9057185,22980186m


So I went on the Moon in hopes that reversing the angle would spoof the Earth location in a similar way, but I am not sure if that what I looking at is really the Earth. Is the Earth visible from the Moon in Google Maps?,125.3519963,22976708m



Can an earth elemental drown/bury its opponent underground?

Problem: how to kill a cleric, and how can the party stop it?

I am DMing in a few days in my brother’s campaign – he is playing my cleric while taking a break from DMing. We’ll turn it back over next session.

  • Notice: I don’t mind killing this PC, since it is the PC I raised from level 1, but the implications of this scenario take a different shape when our Wizard can summon elementals when/if the party reaches level 9. I am also cool with the party thwarting this evil scheme. In fact, I hope that they do since cool is great and we love cool.

The party are in and around the grounds of an elemental cult’s shrine, having defeated any number of evil elementals: gargoyles, salamanders, magma mephits, mud mephits, a water weird. And they slaughtered all of the cultists that they found. The cleric has, unbeknownst to her, contributed to the desecration of the shrine when she stuck a javelin with continual flame burning into the ground (for RP reasons). That makes her the target for plausible reasons …

Proposed method to bury / drown / suffocate my cleric

Earth elemental burrows up out of the ground and grapples a PC. Cleric’s strength is 13, Earth Elemental’s is 20. This is a standard PHB grapple attempt, not a special grapple attack in the monster’s stat block. The problem assumes that the earth elemental is successful in this attempt.

  • Grappled (basic rules, Appendix A)

    A grappled creature’s speed becomes 0, and it can’t benefit from any bonus to its speed.
    The condition ends if the Grappler is incapacitated (see the condition).
    The condition also ends if an effect removes the grappled creature from the reach of the Grappler or Grappling effect, such as when a creature is hurled away by the thunder­wave spell.

  • Moving a grappled creature

    When you move, you can drag or carry the grappled creature with you, but your speed is halved, unless the creature is two or more sizes smaller than you.

  • Salient stat block issues: EE Burrow movement speed is 30. EE has two slam attacks. I think this means that it can try to grapple her twice, or attack one other creature and try to grapple her once.

    you can use the Attack action to make a special melee attack, a grapple. If you’re able to make multiple attacks with the Attack action, this attack replaces one of them.

Two different ways this goes down (yeah, pun intended).

  1. Elemental begins 5′ under the earth’s surface, burrows up (moves 5 or 10 feet), grapples cleric, and then moves 20′ remaining, divided by two, so 10 feet remaining, under ground. Does not leave a hole as far as I can tell.

  2. Elemental encounters the party, engages, and then grabs the cleric with a grapple (assume success), and then moves 15′ down under ground.

    In either case, the cleric begins to deal with the suffocation rules until enough rounds have passed to kill her (with an 18 constitution, she’ll last a little while), or, the party figures out a way to dig her out before she suffocates 5, 10, or 15′ under the ground. She has no burrowing speed.


I am not sure what use her escaping the grapple would be the following round, if she managed it, as she’d still be stuck underground, suffocating, but at least she won’t be going deeper underground. I am not sure if she can cast Guidance on herself to try and escape the grapple, if she’s immersed in earth. It has both verbal and somatic components.

Implications: If this trick works the way I think it does, then when our wizard reaches 9th level we’ll need to get him summon elemental right quick and start trying to drown/suffocate various enemies; our cleric (if she survives) would cast guidance on the elemental when it tries to grapple our foes to help it succeed.

How does the party get her out of this mess?
Does this work like I think it does?
Can a creature who can enter a terrain that another can’t, bring someone into that terrain? I know a water elemental can do this, but most PCs easily enter into water.
Is there a way for her to swim up out of the earth while she is suffocating?

Party composition: (all level 5)

Rogue/Ranger, high elf
Barbarian, Bear, Human
Wizard, High Elf, Evoker
Cleric, Life, Human (not my cleric, another player’s)
Rogue, Arcane Trickster, Gnome
Cleric, Life, Human (My cleric, who may soon take a dirt nap)