a) [tex] \sin(60) - \cos(30) = \frac{ \sqrt{3} }{2} - \frac{ \sqrt{3} }{2} = 0[/tex]
b) [tex] \cos(145) + \cos(35) = 2 \times \cos(90) \times \cos(55) = 2 \times 0 \times \cos(55) = 0[/tex]
c) [tex] \sin(20) - \cos(70) = \sin(90 - 70) - \cos(70) = \cos(70) - \cos(70) = 0[/tex]
h) [tex] { \sin }^{2} (80) + { \sin }^{2} (10) ={ \sin }^{2}(90 - 10) + { \sin }^{2}(10) = { \cos }^{2} (10) + { \sin }^{2}(10) = 1[/tex]
