Question

if cos A =2/5,find the value of 4+4tan2A

Answer 1

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Answer 2

By applying formula,
sec²A-tan²A=1⇒sec²A=1+tan²A and
sec A=1/cos A=1/(2/5)=5/2
4+4 tan²A=4(1+tan²A)=4 sec²A=4(5/2)²=4×25/4=25(Ans.)