2. Two sounds waves travelling in the same direction have y-displacements at time r \text { given by } 2 \sin (\omega t) \text { and } \sin \left(\omega t+\frac{\pi}{2}\right),

\text { where } \omega \text { is constant. } (a) Express the combined wave in the form A sin(or +a). (b) What is the frequency of the combined wave? (c) Find the values of t for which the combined wave has y-displacement 0.