Chapter 5 - Trigonometric Functions - 5.1 Angles - 5.1 Exercises - Page 503: 12

$a)30^0$ $b)120^0$

If two angles are Complement then sum of these angles is $90^0$ If two angles are Supplement then sum of these angles is $180^0$ $a)\alpha+60^0=90^0\Rightarrow \alpha =90^{0}-60^{0}=30^{0};$ $b)\theta+60^0=180^0\Rightarrow \theta=180^{0}-60^{0}=120^{0}$