Trigonometryhard · Past Paper
Value of sin² 5° + sin² 10° + ... + sin² 90° is:
A8
B8.5
C9
D9.5
✓ Correct Answer: D — 9.5
There are 18 terms. 8 pairs sum to 1 (sin² 5 + sin² 85, etc.), plus sin² 45 (0.5) and sin² 90 (1). Total = 8 + 0.5 + 1 = 9.5.
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