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1) You'll need to commit some of these values to memory sin and cos of: 0 30 45 60 90
sin 60 = sqrt(3) / 2 tan 45 = 1 cos 120 = - 1/2 sin 150 = 1/2
2. Area = (1/2) (3^2) sin 45° = (1/2) (9) (sqrt 2) / 2 = (9/4)sqrt 2 units^2
3. tan C = 2.4 = 24/10 = 12/5 = AB/BC
cos A = BC / AC
AC = sqrt ( 12^2 + 5^2) = sqrt (169) = 13
So
cos A = 5/13
4. No question