Find the value of sin² 10 + sin² 20 + sin² 30 + ....... + sin² 80.

A tower standing on a horizontal plane subtends a certain angle at a point 160 m apart from the foot of the tower. On advancing 100 m towards it, the tower is found to subtend and angle twice as before. The height of the tower is

$$ {Cos^4θ +Sin^4θ}={2 \over3} $$ then the value of $$ {Cos^2θ -Sin^2θ+1}$$?

If cos²α + cos²β = 2, then the value of tan³ α + sin⁵ β is :

Fill in the blanks:
Sin A = ____ × (Cos A) 

If $$ sin θ ={20 \over 29}$$, then what is the value of sec θ sin θ?

Solve the given equation.
$$ {{cot \ 30°}\over {1+sin\ 45°}}+{{1+sin\ 45°}\over cot \ 30°}=?$$

The minimum value of 16 tan² θ + 25cot² θ is