Question

Help please: trig!
Find exactly the 2 principal angles you would use to find solutions to: 2cos(3(x- π/4 ))=√3

Answer 1

start with this
\[\cos \theta = \frac{\sqrt{3}}{2}\]
which 2 angles solve this?

Answer 2

30 and 150?

Answer 3

correct
now sub back in stuff in the cosine
\[3(x-45) = 30\]
solve for x
repeat for the 150 to get 2nd solution

Answer 4

So I sub in 30 into 3(x-45)=30 to get my first principle angle?

Answer 5

no sorry i wasn't clear
\[\cos \theta = \frac{\sqrt{3}}{2}\]
\[\theta = 30,150\]
however from the original equation,
\[\theta = 3(x-45)\]
therefore
\[3(x-45) = 30,150\]
solve for "x" .... nothing to sub in

Answer 6

Aaah, I see. Thank you!