Mathematics

Question

16. The value of sin² 5° + sin² 10° + sin² 15° + … + sin² 90° is equal to


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  • Answer:

    11.5

    Step-by-step explanation:

    Let think mathematically. We have a finite series.

    sin² 5° + sin² 10° + sin² 15° + … + sin² 90° . Remeber that sin is a periodic function, and we also know that

    [tex] \sin {}^{2} (45 + 45) = 1[/tex]

    and

    [tex] \sin {}^{2} (30 + 60) = 1[/tex]

    also that

    [tex] \sin {}^{2} (0 + 90) = 1[/tex]

    I'm imying that two angles that add up to 90 will make cancel out to 1.

    Our full series will be

    Angle measures increasing by 5 so

    85+5=1

    80+10=1

    75+15=1

    70+20=1

    65+25=1

    60+30=1

    55+25=1

    50+30=1

    sin^2(45) is the same as sin(45)sin(45)=1/2.

    And sin^2(90)=1 So our value is 9.5