Sine & cosine of obtuse angle
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When two angles are supplementary, their sines and cosines are equal but the cosine values have the opposite sign. If the sine or cosine of one angle is known, the other angle can be found by taking 180 degrees minus the known angle. For example, if sin x = sin 45 degrees, then x = 135 degrees, as 135 degrees and 45 degrees are supplementary.
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Sine & cosine of obtuse angle
- 2. ? When two angles are supplementary their sines are same sin x?=sin( 180- x)? B ? ? x? ? A C ? 180-x
- 3. ? Find sin x? x? sin x?= sin(180-x) = 3 5 5 4 3 180-x
- 4. Eg: If sin x= sin 45 ?, find the value of x sinx= sin(180-x) =sin (180-45) x= 135 ?
- 6. Use calculator to complete the following statements a) Cos 30?= b) cos 150?= 150?= _____- 30?
- 7. ? When two angles are supplementary their cosines are same, (ignoring the sign) cos x?= -cos( 180- x)? B x? A C 180-x
- 8. ? Find sin x? x? cos x?= -cos(180-x) = - 4 5 5 4 3 180-x
- 9. Eg: If cos x= - cos45 ?, find the value of x cos x= - cos(180-x) = - cos(180-45) x= 135 ?
- 10. 12 8 7 10 4 7