If A+B+C = 180 degree then prove that tanA/2 tanB/2+ tan B/2 tanC/2 + tan C/2 tan D/2 = 1 .

If A+B+C = 180 degree then prove that tanA/2 tanB/2+ tan B/2 tanC/2 + tan C/2 tan D/2 = 1 .

Matching exercise

Match the items on the right to the items on the left.

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STEP 4