Q14 of 143 Page 6

Write the value of tan 10° tan 15° tan 75° tan 80°.

tan 10° × tan 15° × tan 75° × tan 80°

= tan 10 × tan 15 × tan(90-75) × tan (90-80)
= tan10 × tan15 × cot 15 × cot10
As we know,

tan θ × cot θ = 1
So,
tan 10 × cot 10 × tan 15 × cot 15
= 1

Write the acute angle θ satisfying √3 sin θ = cos θ

Write the value of cos 1° cos 2° cos 3°…. cos 179° cos 180°.

If A + B = 90° and tan A = 3/4, what is cot B?

If tan A = 5/12, find the value of (sin A + cos A) sec A.