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- The solid in the diagram was formed by removing a corner from a cube with side lengths of 24cm. The length of EB of 6cm. Calculate the measure of angle PER

Dont know how to set up the Cosine Equation to solve this...

StarStrike Feb 14, 2019

#1**+1 **

Check page 7 of this. If it is confusing, I will try to work you through the process.

http://missharvey.weebly.com/uploads/4/4/8/2/4482376/t3.pdf

penquino21 Feb 14, 2019

#3**+1 **

After 2 hours:

RE^2 =18^2+24^2 (24 side length- 6 BE= 18)

RE=30

PR^2=24^2+24^2

PR=33.94112.....

Cos(PER)=30^2+30^2-33.9411...^2 / 2 (30) (30)

cos(PER) = 0.36

acos (0.36) = Angle PER

PER = 68.899803975907 degrees

HOPE THIS IS IT....... Please confirm

StarStrike Feb 14, 2019

#4**+2 **

Conside the line from E to RC that is parallel to BC. Let the point of intersection be X

EX=24

XR=24-6=18

find ER

\(ER=\sqrt{24^2+18^2}\\ ER=\sqrt{900}\\ ER=30 \)

Now PR is just the diagonal of one side of the square

\(PR=\sqrt{24^2+24^2}\\ PR=\sqrt{1152}\\ \)

Now I have all 3 sides of the triangle so I can use cosine rule to find the angle between them

the sides are \(30, \quad30, \quad \sqrt{1152}\)

\(1152=900+900-2*900*Cos(PER)\\ 1152=1800-1800*Cos(PER)\\ -648=-1800*Cos(PER)\\ 0.36=Cos(PER)\\ \angle{PER}=cos^{-1}0.36=68.8998^\circ=68^\circ54' \)

That is assuming I've not made any stupid mistakes.

Melody Feb 14, 2019