Others Maths Puzzle Numerical Ability Averages

if1.sinx+sin2x=1,then cos2x+xos4x=?

a)1 b)3 c)0 d)none

Read Solution (Total 2)

if we take x=pi/2 then sin(pi/2)+2sin(pi/2)cos(pi/2)=1+2(1)(0)=1
so cos2x+cos4x=cos(pi)+cos(2pi)=-1+1=0.
so,ans is(c)
12 years agoHelpfull: Yes(4) No(8)

sinx=1-sin2x=cos2x
therefore... sin2x=cos4x
so,
cos2x+cos4x=1
8 years agoHelpfull: Yes(0) No(0)

Others Other Question

In a village, friendship among girls is mutual. Each girl has either exactly one
friend or exactly two friends among themselves. One morning, all girls with two
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two friends wear hats of different colours. In the afternoon, 10 girls change their
red hats into blue hats and 12 girls change their blue hats into red hats. Now it
turns out that any two friends wear hats of the same colour. How many girls are
there in the village? (A girl can only change her hat once.) the number 80 is divided into four so that if 3 is added to the first ,3 is subtracted from second,the third is multiplied by 3 and the fourth is divided by 3 all the give the same value . the lowest number is 5, what is the highest number?