Sketch the graphs of the following functions: (i) h (x) = 2 sin 3x, 0 ≤ x ≤ 2π/3 (ii) ϕ (x) = 2 sin (2x – π/3), 0 ≤ x ≤ 7π/3
Sketch the graphs of the following functions: (i) h (x) = 2 sin 3x, 0 ≤ x ≤ 2π/3 (ii) ϕ (x) = 2 sin (2x – π/3), 0 ≤ x ≤ 7π/3

    \[\left( \mathbf{i} \right)~h\text{ }\left( x \right)\text{ }=\text{ }2\text{ }sin\text{ }3x,\text{ }0\text{ }\le \text{ }x\text{ }\le \text{ }2\pi /3\]

Since,

    \[g\text{ }\left( x \right)\text{ }=\text{ }sin\text{ }x\]

is a periodic function with period

    \[2\pi .\]

Therefore,

    \[h\text{ }\left( x \right)\text{ }=\text{ }2\text{ }sin\text{ }3x\]

is a periodic function with period

    \[2\pi /3.\]

Hence, we draw the graph of

    \[h\text{ }\left( x \right)\text{ }=\text{ }2\text{ }sin\text{ }3x\]

in the interval

    \[\left[ 0,\text{ }2\pi /3 \right].\]

The values of  

    \[h\text{ }\left( x \right)\text{ }=\text{ }2\text{ }sin\text{ }3x\]

at various points in

    \[\left[ 0,\text{ }2\pi /3 \right]\]

are listed in below:

The curve is:

RD Sharma Solutions for Class 11 Maths Chapter 6 – Graphs of Trigonometric Functions image -3

    \[\left( \mathbf{ii} \right)~\phi \text{ }\left( x \right)\text{ }=\text{ }2\text{ }sin\text{ }\left( 2x\text{ }-\text{ }\pi /3 \right),\text{ }0\text{ }\le \text{ }x\text{ }\le \text{ }7\pi /3\]

Since,

    \[f\left( x \right)\]

is a periodic function with period

    \[T\]

, then

    \[f\text{ }\left( ax\text{ }+\text{ }b \right)\]

is periodic with period

    \[T/\left| a \right|.\]

Therefore,

    \[\phi \text{ }\left( x \right)\text{ }=\text{ }2\text{ }sin\text{ }\left( 2x\text{ }-\text{ }\pi /3 \right)\]

 is a periodic function with period

    \[\pi .\]

Therefore, we draw the graph of

    \[\phi \text{ }\left( x \right)\text{ }=\text{ }2\text{ }sin\text{ }\left( 2x\text{ }-\text{ }\pi /3 \right),~\]

in the interval

    \[\left[ 0,\text{ }7\pi /5 \right].\]

The values of

    \[\phi \text{ }\left( x \right)\text{ }=\text{ }2\text{ }sin\text{ }\left( 2x\text{ }-\text{ }\pi /3 \right),~\]

at various points in

    \[\left[ 0,\text{ }7\pi /5 \right]\]

are listed in below:

The curve is:

RD Sharma Solutions for Class 11 Maths Chapter 6 – Graphs of Trigonometric Functions image - 4