Answer: Since 10° is less than 90, we can express this in terms of a co-function. cos(θ) = sin(90 - θ) cos(10) = sin(90 - 10) cos(10) = sin(80)
Step-by-step explanation: Note that cos10° is periodic: cos (10° + n × 360°) = cos 10 degrees, n . There are more formulas for the double angle (2 × 10°), half angle ((10/2)°) as well as the sum, difference and products of two angles such as 10° and β.