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If cos x = 3/7; x is an angle in the fourth quadrant; what is cos(x/2)?

Science & Mathematics by Anonymous 2018-06-24 17:35:25

Social Science

If cos x = 3/7; x is an angle in the fourth quadrant; what is cos(x/2)?

1 answer

  • Anonymous

    cos( arg(3 - i 2√10) ) = cos(x) = 3/7 The first* complex number that squares to 3 - i 2√10 is -√((7+3)/2) + i √((√7-3)/2) which is -√5 + i√2, with a modulus of √7. cos(x/2) = cos( arg(-√5 + i√2) ) = -√5 / √7 = -√⁵∕₇

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