Question

The figure shows the graph of senx and sen2x

The graph that corresponds to senx + sen2x is:
( I don't know if i have to use the identity sin(x+2x), because, i don't find the answer)

Answer 1

\[\sin(x +2x) = (sinx)\cos2x+(cosx) \sin 2x\]

Answer 2

even so, the is not answer in the options ( i think so)

Answer 3

there*

Answer 4

I think you should try to add the heights of the two graphs and convince yourself of what the answer is.

Answer 5

Approximatively that is.

Answer 6

but look https://www.wolframalpha.com/input/?i=%28sinx%29cos2x%2B%28cosx%29sin2x

Answer 7

i would say be, but why the graph is not according to the answer

Answer 8

B*

Answer 9

Because sin(x) + sin(2x) is not the same as sin(3x).

Answer 10

For example let x = pi/2. Then sin(x) + sin(2x) = 1 + 0 = 1, but sin(3x) = -1.

Answer 11

yeah i see your point

Answer 12

what i mean is, i wrote down in a bad way on wolfram alpha, so wolfram is graphing sin of 3x

Answer 13

?

Answer 14

Because you wrote an alternative representation for sin(3x), it's not surprising that sin(3x) is being graphed. If you wanted the right graph, you could have just written sin(x) + sin(2x).

Answer 15

THanks a lot bro !

Answer 16

welcome bro!

Answer 17

now I'm going to see if i was right with the B answer