The following figure show a semi circle with radius AO=1. A

The following figure show a semi circle with radius AO=1. A C D B O theta/2 theta Use the formula tan=pi/2=(sin theta)/(1+cos theta) to show that: (i) tan 15=2/(2+akar(3))=2-akar(3). (ii) tan 22,5=akar(2)-1.