If θ is a positive acute angle and tan2θ tan3θ = 1
find the value of (2cos2\(\frac{5θ}{2}-1\)).
Answer & explanation
Correct answer: option 3
If tan2θ tan3θ = 1
than 2θ + 3θ = 90°
θ = 18°
Put in find out
(2cos2\(\frac{18\;×\;5}{2}\;-\;1\))
= 2 × (\(\frac{1}{\sqrt {2}}\))2 - 1
= 2 × \(\frac{1}{2}\) - 2
= 0