A rectangular lamina ABCD has sides AB=CD=2a and BC=AD=a . The midpoint of CD is M and the midpoint of BM is N . THe lamina is folded along BM such that the planes BMC and BMDA are perpendicular . For this folded lamina , find in terms of surds if necessary .
(a) AN
(b) AC
(c) angle ACB
This is what i did :
(a) BM =
,
, AB=2a
AM=AB=2a , cos angle MBC
angle MBC=45 degree , therefore ABN= 45 degree
(b) AMC=90 degree
MC=a , AM = 2a
(c) ABC=90
tan angle ACB = 2a/a
ACB=arctan 2
= 63 degree 26 mins
CAn somepne pls check my working . Thanks a lot !!