36sin3A - cos3A = (sinA-cosA)(1 + sinA.cosA) ≠(sinA - cosA)(sinA + cosA)(sin4A + cos4A)
or simply, put A = 45°.... u won't get them equal...!!
3 Answers
36
1putting value of A 45° we get
l.h.s
1/8-1/8=..
r.h.s
(1/2-1/2)(,...)=0';;;;
i.e qstn is crrct
3a3 - b3 = (a-b)(a2 + ab - b2)
put a as sinA and b as cosA.
sin3a - cos3a = (sinA - cosA)(1 - sinA*cosA).
and it is given that this is equal to (sinA - cosA)(sinA + cosA)(sin4A + cos4A)
and as far as i can see these are not equal.
put a = 30 degrees.
and then LHS = 1/8 - 3*root3/8.
RHS = (1/4 - 3/4)(1 - 2*1/4*3/4) = -1/2(5/8) = -5/16.
HENCE LHS ≠RHS.