Trigonometric equations: \(\displaystyle{3}{\sin{{B}}}+{4}{\cos{{C}}}={6}\) and \(\displaystyle{4}{\sin{{C}}}+{3}{\cos{{B}}}={1}\) show that \(\displaystyle{\sin{{\left({B}+{C}\right)}}}={0.5}\)

Tiffany Maldonado

Tiffany Maldonado

Answered question

2022-04-09

Trigonometric equations:
3sinB+4cosC=6
and
4sinC+3cosB=1
show that
sin(B+C)=0.5

Answer & Explanation

anita1415snck

anita1415snck

Beginner2022-04-10Added 19 answers

(3sinB+4cosC)2=62=9sin2B+24sinBcosC+16cos2C=36
(4sinC+3cosB)2=12=16sin2C+24sinCcosB+9cos2B=1
Add the two equations
16+9+24(sinBcosC+sinCcosB)=37
sinBcosC+sinCcosB=12
sin(B+C)=12

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