Question

If A is an acute angle and SinA =cosA , find 3tan²A+ cos_{​​​​^​​​​​​​​^2-1}

Answer 1

Since

Sin A = Cos A
Sin A = √1-Sin²A

Squaring both sides

Sin²A = 1- Sin²A
2Sin²A = 1
Sin²A = 1/2
Sin A = 1/√2
=> A = 45°

Therefore 3tan²A+ Cos²A - 1 = 3 x 1 + 1/2 - 1

= 5/2