trig-TI83

# Example5 convert 8º34 65 to radians rounded to the

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Example#5: Convert 8º34 ' 6.5 " to radians rounded to the 5th decimal place. 1. Type 8º34'6.5"º and ENTER . This works because the 8º34'6.5" will return the angle in degrees. Then, the º will convert that angle to the current units, radians. 2. It returns ".1495480521". Thus, the answer is 0.14955 . Trigonometric Functions Sine, Cosine, & Tangent : Example#6: Approximate cos(3 π /4) on the calculator. 0. By hand, the answer is = -0.707106781187 . 1. Type COS(3 π /4) ENTER . The parenthesis are needed so that the division is done before the cosine function. 2. It returns "-.7071067812". If you didn't get this, make sure you're in radian mode or use the r function. Example#7: Approximate tan35º on the calculator. 1. Type TAN(35º) ENTER . 2. It returns ".7002075382" no matter what mode the calculator is in. Example#8: Appr. sin 2 (-30º). 1. Type SIN(-30º) 2 ENTER . 2. It returns ".25".

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Secant, Cosecant, & Cotangent : Example#9: Appr. csc(4 π ). 0. By hand, csc(4 π ) is undefined. 1. Type 1/SIN(4 π ) ENTER . DON'T USE SIN -1 . That's the inverse sine function. 2. It returns "-5E12". Why? 3. How might you tell when to trust the calculator and when not to? Cosecant and cotangent are evaluated in similar ways. Inverse Trig. Functions : Example#10: Appr. cos -1 (-.5) in radians. 0. By hand, cos -1 (-.5)=2 π /3=2.09439510239 . 1. Type COS -1 (-.5) ENTER . Note COS -1 is in yellow over the COS key. 2. It returns "2.094395102". Example#11: Appr. tan -1 (1) in degrees. 1. If you just type TAN -1 (1) ENTER , you'll get ".785398163397" because inverse trig. functions return an angle in the current setting, radians. 2. Change to degree mode. 3. Execute the command TAN -1 (1) . If it is the last command from step 1, you can just press ENTER . 4. It now returns "45". Thus, the answer is 45º. 5. Change back to radian mode. As long as you use the º function, this is one of the few times you will have to go to degree mode. Inverse sine is used the same way. Polar and Rectangular forms: Complex numbers Mode Setting : 1. Press MODE . 2. The 7th option sets whether any commands can return complex numbers returns Real : an error a+b i : rectangular mode, i.e. 5-7 i or re^ θ i : exponential polar form, i.e. 3(cos(0.56)+ i sin(0.56))=3e^(.56 i ) This works because you would find it higher math classes that r*e^ θ i =r(cos( θ )+ i sin( θ )).
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