Question Number 211392 by CrispyXYZ last updated on 08/Sep/24
$$\bigtriangleup{ABC}.\:\mathrm{cos}\:{C}=\frac{\mathrm{sin}\:{A}\:+\:\mathrm{cos}\:{A}}{\mathrm{2}}=\frac{\mathrm{sin}\:{B}\:+\:\mathrm{cos}\:{B}}{\mathrm{2}}. \\ $$$$\mathrm{Find}\:\mathrm{cos}\:{C}. \\ $$
Answered by Frix last updated on 08/Sep/24
$$\mathrm{Rectangular}\:\mathrm{triangle} \\ $$$$\mathrm{cos}\:{A}\:=\mathrm{sin}\:{B}\:\wedge\:\mathrm{sin}\:{A}\:=\:\mathrm{cos}\:{B}\:\Rightarrow\:{C}=\mathrm{90}° \\ $$