Question

Trigonometry question on R cos (theta - alpha). http://d.pr/L96v

Answer 1

Second part of the question is what i need help with.

My answer to the first part:

\[\sqrt{17} \cos (\Theta + \alpha)\]

Second part:

My answers are:

46.9 and -46.9. But answers says: 46.9 and -75?

Answer 2

Edit: I mean to write, the answer to my first answer was √cos(Θ+14)

Answer 3

[r\sin(x+\theta)\] where
\[r=\sqrt{a^2+b^2}, \tan(\theta)=\frac{a}{b}\]if i recall correctly

Answer 4

oops you want cosine, sorry

Answer 5

same idea but this time
\[r\cos(x - \theta)\] same r but
\[\tan(\theta)=\frac{b}{a}\]

Answer 6

so we need
\[\theta\] in degrees i take it, yes?

Answer 7

yes

Answer 8

i get
\[\theta = -14.4\] giving
\[\sqrt{17}\cos(x+14.4)\]

Answer 9

\[\sqrt{17}\cos(x+14.4)=2\]
\[\cos(x+14.4)=\frac{2}{\sqrt{17}}\]
\[x=\cos^{-1}(\frac{2}{\sqrt{17}})-14.4\]

Answer 10

between -180 and 180 degrees.

Answer 11

Mark scheme: http://d.pr/ubFq

Where does the value -75 come from?