PreCalc 2 · Trigonometric Functions
Check the mode. Degree problems need degree mode. Radian problems need radian mode. Round to 3 decimal places.
Mode first
If the angle has a degree symbol, use DEG. If the angle is in π or a plain number of radians, use RAD.
Wrong mode is the most common calculator mistake.
Example
sin 20° in degree mode is about 0.342.
sin 20° is about 0.342. Check that on your calculator.
Degree mode. sin 20°.
Answer: 0.342
Find sin 50°. Round to 3 decimal places.
Degree mode.
0.766
Answer: 0.766
Find cos 10°. Round to 3 decimal places.
Degree mode.
0.985
Answer: 0.985
Find tan 15°. Round to 3 decimal places.
Degree mode.
0.268
Answer: 0.268
Find cos 70°. Round to 3 decimal places.
Degree mode.
0.342
Answer: 0.342
Find sin 80°. Round to 3 decimal places.
Degree mode.
0.985
Answer: 0.985
Find sin 1, with 1 in radians. Round to 3 decimal places.
Radian mode.
0.841
Answer: 0.841
Find cos 2 (radians). Round to 3 decimal places.
Radian mode.
-0.416
Answer: -0.416
Find tan 0.5 (radians). Round to 3 decimal places.
Radian mode.
0.546
Answer: 0.546
Find sin 140°. Round to 3 decimal places.
Degree mode.
0.643
Answer: 0.643
Find cos 200°. Round to 3 decimal places.
Degree mode.
-0.940
Answer: -0.940
Find tan 110°. Round to 3 decimal places.
Degree mode.
-2.747
Answer: -2.747
Find csc 25°. Round to 3 decimal places.
csc = 1/sin.
Degree mode. 1 / sin 25°.
2.366
Answer: 2.366
Find sec 40°. Round to 3 decimal places.
sec = 1/cos.
1.305
Answer: 1.305
Find sin 400°. Round to 3 decimal places.
400° − 360° = 40°.
sin 400° = sin 40°.
0.643
Answer: 0.643
Find cos(−50°). Round to 3 decimal places.
Cosine is even: cos(−θ) = cos θ.
0.643
Answer: 0.643
Find tan 5 (radians). Round to 3 decimal places.
Radian mode.
-3.381
Answer: -3.381
Find cot 35°. Round to 3 decimal places.
cot = 1/tan.
1.428
Answer: 1.428
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