Step-by-step explanation:
Use Sine rule.
[tex] \frac{ac}{ \sin(b) } = \frac{ab}{ \sin(c) } \\ \frac{ac}{ \sin(90) } = \frac{10}{ \sin(42) } \\ ac \sin(42) = 10 \sin(90) \\ ac = \frac{10 \sin(90) }{ \sin(42) } \\ ac = 14.9 \: units \: (3s.f)[/tex]
Angle A + angle B + angle C = 180 (sum of angles in triangle)
Angle A + 90 + 42 = 180
Angle A + 132 = 180
Angle A = 180 - 132
= 48
[tex] \frac{bc}{ \sin(a) } = \frac{ab}{ \sin(c) } \\ \frac{bc}{ \sin(48) } = \frac{10}{ \sin(42) } \\ bc \sin(42) = 10 \sin(48) \\ bc = \frac{10 \sin(48) }{ \sin(42) } \\ = 11.1units (3sf)[/tex]
