Question

solve triangle ABC which have angleC=1250:431;a=4:2cmandc=8:2cmFindangleA

Answer 1

Answer on Question #51010 – Math – Trigonometry

Task: solve triangle ABC which have angle C=125°; a=4cm and c=8cm. Find angle A

Solution

According to the Sine Rule,

$$\frac {a}{\sin A} = \frac {c}{\sin C} \Rightarrow \sin A = \frac {a}{c} \sin C \Rightarrow A = \arcsin \left(\frac {a \sin C}{c}\right) = \arcsin \left(\frac {4 \sin 125^0}{8}\right) = \arcsin (0.4096) \approx 24.18^0$$

where $\arcsin(t)$ is the inverse of sine function $\sin(t)$.

Answer: A=24.18°.

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