1.

8. It3 cotA 4, check whether+ an C1 - tanAl + tan A

Answer»

(1-tan²A)/(1 + tan²A)=2cos²A -1

3cotA = 4 cotA = 4/3 tanA = 1/cotA = 3/4

LHS = (1-tan²A)/(1+ tan²A) = (1 - 9/16)/(1+ 9/16)= 7/25

RHS =2cos²A -1∵tanA = 3/4 ∴cosA = 4/5

= 2(4/5)² -1 = 32/25 -1 =7/25

LHS = RHS so, (1-tan²A)/(1 + tan²A)=2cos²A-1

as cos^2A-sin^2A=2cos^2A-1


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