tanA/2.tanB/2+tanB/2.tanC/2+tanC/2.tanA/2=1 CHỨNG MINH HAI VẾ BẰNG NHAU

Đáp án:

Giải thích các bước giải:

ta co: tan A/2=cotg(B+C)/2

ma cotg(B+C)/2= 1- tanB/2tanC/2

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----------------------------tanB/2+tanC/2

vay tanA/2tanB/2 +tanA/2tanC/2=

tanB/2-- tan^2 B/2tanC/2 + tanC/2-- tanB/2 tan^2C/2

______________________________________________

--------tanB/2+tanC/2

= 1--- tanB/2tanC/2

vay tan A/2tanB/2 +tanA/2tanC/2+ tan B/2tanC/2=1--tanB/2tanC/2+tanB/2tanC/2=1

dpcm