Find the exact value of the expression cos10°cos20°-sin10°sin20°

In the field of thermodynamics, rankine is the unit used to measure temperature. one can convert temperature from celsius into rankine using the formula c= r/1.8 - 273, what is the temperature in celcius corresponding to r degrees rankine.

Write two subtraction equations that are equivalent to 5 + 12 = 17.

Determine the number of outcomes in the event. decide whether the event is a simple event or not. upper a computer is used to select randomly a number between 1 and 9 comma inclusive. event upper b is selecting a number greater than 4. event upper b has nothing outcome(s). is the event a simple event? (yes or no) because event upper b has (fewer than, exactly, more than) one outcome.