So base on your question the possible answer to that kind of question and the solution are the following and i hope you will understand the formula and free to ask some questions if needed.
<span>2<span>cos2</span><span>x2</span>=1+cosx=1−<span>1517</span>=<span>217</span>,<span>cos2</span><span>x2</span>=<span>117</span></span>
<span>cos<span>x2</span>=−<span>1<span>17<span>−−</span>√</span></span>....(1)</span>
<span>sin<span>x2</span>=<span>1<span>17<span>−−</span>√</span></span>,90<<span>x2</span><135</span>
<span>sin<span>x2</span>>0,cos<span>x2</span><0,tan<span>x2</span><0</span>
<span>2<span>sin2</span><span>x2</span>=1−cosx=1−<span><span>−15</span>17</span>=<span>3217</span>,sin<span>x2</span>=<span>4<span>17<span>−−</span>√</span></span>.....(2)</span><span>
divide (2) by (1) and get the value of tan x/2</span>
5578/68=82.029411764705882352941176470588
that would be rounded to 82.02 which is the answer
4y-y is NOT equivalent to 4.
4 is multiplied by 'y', and then 'y' is subtracted from that equation. Even if y=1, your equation would look like 4x1-1=3.
Hope that made sense:)
The answer is D, Cavalieri's Principle
