HCF of 252 sec 308 Sec.198 Sec

The HCF of 252 and 308 is :

The time period of a seconds pendululm is measured repeatedly for three times by two stop watches A, B . If the readings are as follows {:("S.NO.", A, B)(1, 2.01 "sec", 2.56 "sec"),(2, 2.10 "sec", 2.55 "sec"), (3, 1.98 "sec", 2.57 "sec"):}

The time period of a seconds pendulum is measured repeately for the times by two stop watches. A,B if the readings are as follows, then {:(S.NO,A,B),(1.,20.1 sec,2.56 sec),(2., 2.10sec,2.55 sec),(3.,1.98 sec,2.57sec):}

The time period of a seconds pendululm is measured repeatedly for three times by two stop watches A, B . If the readings are as follows {:("S.NO.", A, B)(1, 2.01 "sec", 2.56 "sec"),(2, 2.10 "sec", 2.55 "sec"),(3, 1.98 "sec", 2.57 "sec"):}

Show that the coordinates of the orthocentre of DeltaABC is : ((x_1 a sec A + x_2 b sec B + x_3 c sec C)/(a sec A + b sec B + c sec A)), (y_1 a sec A + y_2 b sec B + y_3 c sec C)/(a sec A + b sec B + c sec C))

(sec 2A+1 ) sec ^(2) A= ................. A) sec A B) 2 sec A C) sec 2A D) 2 sec 2A

The value of sec20+sec40+sec160 is