Let m∠V=120∘ and mPQ⌢=40∘. We have the formula for the angle formed by two tangents drawn to a circle from an exterior point:
m∠V=21(mPTQ⌢−mPQ⌢) where PTQ is the major arc and PQ is the minor arc. The entire circle is 360∘, so mPTQ⌢=360∘−mPQ⌢=360∘−40∘=320∘. Then
120∘=21(320∘−40∘)=21(280∘)=140∘. This is a contradiction! Therefore, we must consider the tangents to intersect at R.
Let x be the mTQ⌢. Then m∠R=21(mPQ⌢−mTQ⌢) 40∘=21(mPQ⌢) so mPQ⌢=2∗40∘=80∘. Also mPT⌢+mTQ⌢+mPQ⌢=360∘. We also know that
m∠V=21(mPT⌢−mTQ⌢) 120∘=21(mPT⌢−mTQ⌢). Thus, 240∘=mPT⌢−mTQ⌢. We have mPT⌢+mTQ⌢+40∘=360∘. mPT⌢+mTQ⌢=320∘. So, mPT⌢=320∘−mTQ⌢. 240∘=320∘−mTQ⌢−mTQ⌢. 2mTQ⌢=320∘−240∘=80∘. mTQ⌢=40∘. Therefore mPT⌢=320∘−40∘=280∘. The question asks for angle R.
m∠R=21(mPT⌢−mPQ⌢)=21(280∘−80∘)=21(200∘)=100∘.