Simplify the expression by using a double angle formula

cos^2 4theta-sin^2 4theta

Adepartment store purchases screen-printed t-shirts at a cost of $5 per shirt. they mark up the price 150% (making the selling price 250% of the store's purchase price) and put them on the sales floor. every month that a t-shirt doesn't sell, the store reduces the selling price by 25%.

Sum of the interior angles of a pentagon

Given right triangle abc, what is the value of tan(a)?