<ol>
<li><p>Yeah - I don’t think this one is solvable without more info. The trig functions (sin/cos) are missing the argument; all we see is sin and cos (as opposed to sine of an angle).
Edit: theta. However there is no diagram and we have no idea what theta is or where R is.</p></li>
<li><p>The bolded formula is exactly the law of cosines. Note: Use ^ for exponents, i.e. c^2 = 5^2 + 7^2 - 2<em>5</em>7 cos 110º.</p></li>
<li><p>This is a badly typed question. I solved it interpreting it as sin 2x and cos 2x, and there are two possible answers: ±sqrt(3)/4. Then I read it as sin^2 x and cos^2 x, and the answer is 1/4 (not 1/16). Then after looking at the solution, I believe the question is supposed to be interpreted as:</p></li>
<li><p>If sin 2x = 1/2, what is (sin^2 x)(cos^2 x)?</p></li>
</ol>
<p>Only THEN the answer is 1/16. </p>