Inverse Cos and Tan

In the same way that we can find an unknown angle from the sin ratio (opposite:hypotenuse), we can do the same with cos and tan.

angle V and W and three sides: 2, 3 and 3.6 cm By definition, cosV° = adjacent ÷ hypotenuse
= 2 ÷ 3·6
= 0·556

We can find V° by telling our calculator that 0·556 is the cos of V°, and it will tell us V if we use inverse-cos. Try this:

[inv] [cos] [0] [·] [5] [5] [6] [=]
56.2° - close enough.

We can find W° in a similar way:
tan W° = opposite ÷ adjacent = 2 ÷ 3 = 0·666
W° = inverse-tan 0·666 = 33·7°

Our answers are slightly inaccurate due to rounding.