i have problem in learning formula of trigo. how would i learn them

<$1$2>Only remember the formula of sin2x, sin(a + b), sina sinb (Similarly for the cos & tan)<$1$2>You can easily prove the rest formula by using this.<$1$2><$1$2>Thanks & Regards<$1$2>Jitender Singh<$1$2>IIT Delhi<$1$2>askIITians Faculty