C3 Trig help

Use the answer you got in the previous part. Make a substitution for the 4cos.....bit with the answer you found before and consider that

$\displaystyle -1 \leq \cos (\theta) \leq 1$ so $\displaystyle \cos (\theta)=1$ will correspond to the maximum value. And similarly you can use -1 for the min values.

You've lost me sorry.

Okay I didn't read the whole question as I (wrongly) assumed it was like a question I had seen before.

Okay so the maximum value is going to be 25 because you have 25 minus the thing you found earlier which a function of cos so you set cos theta =0 and you have 25-0=25 so that is the max. (Since it is a squared term you know it must be a max.)

so your term in cos theta must be equal to zero, you can solve this to get the angle you need.

Similarly for the second part the min is going to be 25 minus the biggest thing you can make the part found earlier this is when cos theta =1, you can then solve this like before to find the other angle.