Tan 70-Tan 20 =2 Tan 50
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Answer:
Step-by-step explanation:
consider Left hand side:
tan70 = sin70/cos70
tan20 = sin20/cos20
sin70/cos70 - sin20/cos20
taking LCM:
(sin70cos20 - sin20cos70)/cos70cos20
(SINCE: sinAcosB-sinBcosA=sin(A-B)
sin(70-20)/cos70cos20 = sin50/cos70cos20
NOW :
cos70 = sin20 (SINCE: cos(90-70) = sin20)
sin50/sin20cos20
MULTIPLY AND DIVIDE BY 2:
2sin50/2sin20cos20
(SINCE: 2sinacosa = sin2a):
2sin50/sin2*20
2sin50/sin40
(SINCE: sin40 = cos50):
2sin50/cos50
= 2tan50
As LHS = RHS
hence proved
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