Answer:
Step-by-step explanation:
a=0 if both x and y are each =0
for all other real values a>0
Point a would lie at the same point from the beginning.
EXPLANATION
say point a is x,y. Reflecting over the y axis makes it -x, y. Reflecting over the x axis makes it -x, -y. Finally rotating it 180 degrees would make it x,y, the same spot as in the beginning.
Cot(-x) = 1 / tan(-x)
Tan(-x) * 1 / tan(-x) = 1
The sample space (list of outcomes) is:
DFNR; DFRN; DRFN; DRNF; DNFR; DNRF;
NFDR; NFRD; NRFD; NRDF; NDRF; NDFR;
RFDN; RFND; RNFD; RNDF; RDFN; RDNF;
FRDN; FRND; FNRD; FNDR; FDRN; FDNR
P(Dave beside Natalie) = 1/2
P(B,G,B,G or G,B,G,B) = 1/3
P(boys in the middle) = 1/6
P(Frida beside Natalie) = 1/2
P(Robbie between Frida & Natalie) = 1/6
P(Natalie between Dave & Robbie) = 1/6
Explanation
Letting D=Dave, R=Robbie, N=Natalie, and F=Frida you get the list of possibilites above.
For P(Dave beside Natalie), look for DN or ND. This appears 12 times out of the 24 possibilities above; 12/24 = 1/2.
For P(B,G,B,G or G,B,G,B), we have the possibilities DFRN, DNRF, RFDN, RNDF, FRND, FDNR, NDFR, NRFD. There are 8 possibilites out of 24; 8/24 = 1/3.
For P(Frida beside Natalie), look for NF or FN. This appears 12 times out of the 24 possibilities; 12/24 = 1/2.
For Robbie between Frida and Natalie, look for FRN or NRF. This appears 4 times out of 24; 4/24 = 1/6.
For Natalie between Robbie and Dave, look for RND or DNR. This appears 4 times out of 24; 4/24 = 1/6.
