倍角公式问题已知tanx=2,则tan2(x-π/ - 知识问答

倍角公式问题已知tanx=2,则tan2(x-π/4)等于A.4/3 B.-4/3 C.3/4 D.-3/4

2个回答

tan(x-π/4)
=(tanx-tanπ/4)/(1+tanxtanπ/4)
=(2-1)/(1+2)
=1/3
tan2(x-π/4)
=2tan(x-π/4)/(1-tan²(x-π/4))
=2×(1/3)/(1-(1/3)²)
=3/4

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