Answer:
[tex] \because \: \cos \theta = \sin \: (90 \degree - \theta) \\ \\ \therefore \: \cos \: 42 \degree = \sin \: (90 \degree - 42 \degree) \\ \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = \sin \: 48 \degree \\ \\ \: \: \: \: \: \: \: \: \: \: \: \orange{ \boxed{ \therefore \: \cos \: 42 \degree =\sin \: 48 \degree}}[/tex]
